18.) B
solution
P = B x R 40% = .4
= 85 x .4
= 34 teenagers
19.) C
solution
B = P / R 30% = .3
= 12 / .3
=40 volunteer doctors
20.) B
solution
first solve for daily income
B = P / R 40% = .4
= Php600 / .4
= Php1,500
then solve for children's allowance rate
R = (P / B) x 100
= Php225/Php1,500 x 100
= 0.15 x 100
= 15%
This will help you.