function solve(arr) {

    let map = new Map();
    for (let string of arr) {
        let tokens = string.split(' ');
        let name = tokens[0];
        let grades = tokens.splice(1, tokens.length).map(Number);

        if (!map.has(name)) {
            map.set(name, []);
            map.set(name, map.get(name).concat(grades))
        } else {
            map.set(name, map.get(name).concat(grades));
        }
    }

    function average(a, b) {
        let aSum = 0;
        for (let i = 0; i < a[1].length; i++) {
            aSum += a[1][i];
        }
        let bSum =0;
        for (let i = 0; i < b[1].length; i++) {
            bSum+=[1][i];
        }

        let aAverage =aSum/a[1].length;
        let bAverage =bSum/b[1].length;
        return aAverage -bAverage;
    }

    let sorted = Array.from(map).sort((a, b) => average(a, b));

    for(let keys of sorted) {
        console.log(`${keys[0]}: ${keys[1]}, `)

    }

}

solve(['Lilly 4 6 6 5',
    'Tim 5 6',
    'Tammy 2 4 3',
    'Tim 6 6']);