Question

A French class has a total of

Answer 1

If the number of males is x and the number of females is y,
x-13=y
x+y=39. Substituting x-13 for y, we have x+x-13=39 and by adding 13 to both sides we get 52=2x and dividing by 2 we get x=26

Answer 2

F=number of females
m=number of males

total is 39
m+f=39

males is 13 more than females
m=13+f
subbsitute 13+f for m

m+f=39
13+f+f=39
13+2f=39
minus 13 both sides
2f=26
divide both sides by 2
f=13

13 females

m=13+f
m=13+13
m=26

13 females and 26 males