We start by declaring variables for boys and girls:

- Let b be the number of boys
- Let g be the number of girls

- b = g + 5
- b + g = 13

g + 5 + g = 13

Grouping like terms, we get:

2g + 5 = 13

Subtract 5 from each side:

2g + 5 - 5 = 13 - 5

Cancel the 5's on the left side and we get:

2g = 8

Divide each side of the equation by 2 to isolate g:

2g/2 = 8/2

Cancel the 2's on the left side and we get:

g = 4

Substitute g = 4 into equation (1) to solve for b:

b = 4 + 5

b =

**9**