Question 831005
 Lisa and Mike are sister and brother.
Let g = no. of girls
Let b = no. of boys
 Lisa has twice as many sisters as brothers,
2b = g - 1
g = 2b + 1
:
 and Mike has five times as many sisters as brothers.
g = 5(b-1)
g = 5b - 5
g = g, therefore
5b - 5 = 2b + 1
5b - 2b = 1 + 5
3b = 6
b = 6/3
b = 2 boys
then
2(2) + 1 = 5 girls