algo.js

function algorithm(x, y, z, w) {
  var n = 0;

  for (var i = 0; i <= w / x; i++) {
    for (var j = 0; j <= w / y; j++) {
      for (var k = 0; k <= w / z; k++) {
        console.log(i, j, k, '=', i * x + j * y + k * z);
        if (i * x + j * y + k * z === w) {
          n++;
        }
      }
    }
  }

  return n;
}

var res = algorithm(10, 15, 25, 40);

console.log(res);