As there is 5 more girls than boys and b is the number of boys, the expression b + 5 represents the number of girls.
total there are 27 childrens
b + (b+5) = 27
b + b + 5 = 27
2b = 27 -5
b =22 / 2
b =11
so the number of boys there are 11 and girls are 11 + 5 = 16
and total is 16 + 11 = 27