Aproblem states: "there are 7 more girls than boys in a club. there are 23 members in the club in all. how many girls are there in the club? " let g represent the number of girls. which expression represents the number of boys? g+7 g⋅7 g−7 7−g

 
15 girl
b = g-7 

To answer this question, you need to know how to translate the description into an equation. In this case, there is two equation which was: (g=girl, b=boy)
1. g=b+7   
2. g+b=23

The 1st equation can be changed into b=g-7 which was express the number of the boy. If you insert this equation into second you will got the number of girls
g+b=23
g + (g -7)=23
2g= 30
g= 15