var mult =(a,b)=> { // <- you need to add one tab
    var m = a;
    var n = b;
    for (var c=a; c<=b; c++){ // <- you need to add one tab
        if (c % 5===0){ // <- you need to add one tab
            var m = a*c;
            n = b*c;
        } // <- you need to remove one tab
    } // <- you need to remove one tab
    return (m+n);
} // <- you need to remove one tab

console.log(mult(5,5));