Paul has twice as many brothers as sisters.
His sister Mary has five times as many brothers as sisters.
How many sons and daughters do their parents have?
Let B = number of boys.
Let G = number of girls.
Paul has B-1 brothers and G sisters.
. . We are told that: .B - 1 .= .2G
Mary has B brothers and G-1 sisters.
. . We are told that: .B .= .5(G - 1)
Solve the system of equations: .B = 5, S = 2
Answer: .5 sons, 2 daughters