Question 187792
.
Let g = number of girls
then
3g-1 = number of boys
.
g + 3g-1 = 39
4g-1 = 39
4g = 40
g = 10 (number of girls)
.
number of boys:
3g-1 = 3(10)-1 = 30-1 = 29 (number of boys)