13.5484
It is so very simple and quick to get the answer if you use the calculator that comes with your computer. But since you are not able to do so, the answer is 13.5 approx.
310 divided by 4,200 is 0.0738095238095
100
0.0071
4.2
60
140
31
6.2
0.0286
310
600
310 divided by 3 is 103.33 or 103 with remainder 1.
84