Question

the ratio of boys to girls in a class is 4:3 are 35 students in the class how many students are boys

Answer 1

The number of boys in class
=35÷(4+3)(total ratio)×4(ratio of boys)
=20

I am not very good at explaining but I hope it helps ^^

Answer 2

35 : (4 + 3) = 5
5 * 4 = 20 (Boys)
5 * 3 = 15 (Girls)
-----------------
20 + 15 = 35