Question

There are 16 girls in a school club. the number of girls is four more than twice the number of boys. find the number of boys.

Answer 1

The number of boys . . . . . B
Twice the number of boys . . . 2B
4 more than twice the number of boys . . . 2B+4

You said that the number of girls is equal to that, so . . .  G = 2B+4

But you also told us what  G  is:  16 = 2B+4

Subtract  4  from each side:  12 = 2B

Divide each side by  2 :  6 = B

There you have it.  There are  6 boys in the club.