Your answer is 8.4 X 10^7.
Hope this helped!
There is no real shortcut in learning integration formulas. You should take time learning and understanding how the formulas are derived until you are familiar with the formulas and you can easily recall the formulas. Hope this answers the question.
If this is a proportion, then the answer is 16.
3:12, 4:16
3*16=12*4
45 ÷ 3 = 15
21 ÷ 3 = 7
12 ÷ 3 = 4
(4 + 15) x 7 = 133
OR if you’re using bedmas/pedmas
4 + (15 x 7) = 109