Much better, yeah it seemed some little things were missing. Althought your code works, there are uneccessay bits that can be removed (in bold) :

function largestOfFour(arr) {

**arr.sort(function(a,b){**

**return (a-b);});**

var result = [];

for (i=0; i < arr.length; i++){

for(j=0;j < arr[i].length; j++){

arr[i].sort(function(a,b){

return (b-a);});

}

}

for (k=0; k < arr.length; k++){

result.push(arr[k][0]);

}

return result **.reverse()**;

}

largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);