Question 203209
Let M = Mother's age.
A = Alex's age.
S = Sister's age.
A = S-8
M = 2S+6
M = 42, so...
2S+6 = 42 Subtract 6 from both sides.
2S = 36 Divide both sides by 2.
S = 18
A = 18-8 = 10
Alex is 10 years old and his sister is 18 years old.