Clojure Edited

function Solve(input) {
    counter = 0;
    var variables = {};
    var lines = input.map(function (item) {
        item = item.trim();
        return item;
    });

    for (var m = 0; m < lines.length; m += 1) {
        if (lines[m].indexOf('  ') !== -1) {
            lines[m] = lines[m].split(' ').filter(function (n) {
                return n != ''
            }).join(' ');
        }
    }


    for (var i = 0; i < lines.length; i += 1) {
        var currentLine = lines[i],
            operator = '',
            currentVariable = '',
            currentArrayAsString,
            currentArray = [];

        if (lines[i] !== lines[lines.length - 1]) {

            currentVariable = currentLine.substring(currentLine.indexOf('(def ') + '(def '.length,
                currentLine.indexOf(' ', currentLine.indexOf('(def ') + '(def '.length + 1));
        }

        currentArrayAsString = currentLine.substring(currentLine.indexOf
        (currentVariable) + currentVariable.length + 1, currentLine.length - 1);

        if (currentArrayAsString[0] === '(' && currentArrayAsString[currentArrayAsString.length - 1] === ')') {
            currentArrayAsString = currentArrayAsString.substring(3, currentArrayAsString.length - 1)   // edited
        }

        if (currentArrayAsString[0] == '+' ||
            currentArrayAsString[0] == '*' ||
            currentArrayAsString[0] == '/' ||
            currentArrayAsString[0] == '-') {

            currentArrayAsString = currentArrayAsString.substring(1, currentArrayAsString.length).trim();
        }

        currentArray = currentArrayAsString.split(' ');

        for (var j = 0; j < currentLine.length; j += 1) {
            var currentSymbol = currentLine[j];

            if (currentSymbol == ' ') {
                continue;
            }

            if (currentSymbol === '+' || currentSymbol === '-' ||
                currentSymbol === '/' || currentSymbol === '*') {
                operator = currentSymbol
            }
        }

        if (currentArray.length > 0) {
            for (var d = 0; d < currentArray.length; d += 1) {
                var current = currentArray[d].trim();
                if (variables[current] || variables[current] === 0) {
                    currentArray[d] = variables[current];
                }
            }
            currentArray = currentArray.reduce(flatten, []).map(Number);
        }
        counter++;

        // start edit
        var value = getOperation(operator, currentArray);

        if (isNaN(value)){
            return value;
        }

        variables[currentVariable] = value;
        // end edit
    }

    return variables[currentVariable];  // edit

    function flatten(arr, item) {
        if (Array.isArray(item)) {
            return arr.concat(item);
        }
        return arr.concat([item]);
    }

    function getOperation(operator, arr) {

        if (arr.length == 1) {
            return arr[0];
        }

        switch (operator) {
            case '+':
                return sum(arr);
            case '-':
                return subtract(arr);
            case '*':
                return multiplication(arr);
            case '/':
                return division(arr);
            default :
                return arr;
        }
    }

    function sum(arr) {
        var sum = 0;
        for (var i = 0; i < arr.length; i += 1) {
            sum += arr[i];
        }
        return sum;
    }

    function subtract(arr) {
        var differences = 0;
        for (var i = 0; i < arr.length; i += 1) {
            differences -= arr[i];
        }
        return differences;
    }

    function division(arr) {
        var result = arr[0];
        for (var z = 1; z < arr.length; z += 1) {
            if (arr[z] == 0) {
                return 'Division by zero! At Line: ' + counter; // edit
            }
            result = Math.floor(result / arr[z]);
        }
        return result;
    }

    function multiplication(arr) {
        var result = 1;
        for (var i = 0; i < arr.length; i += 1) {
            result *= arr[i];
        }
        return result;
    }
}