posted by Melissa on .
Mario is 16 years older than his sister Mercedes. Together, their ages total 36 years. How old is Mercedes?
Mercedes is 20 years old.
let x = Mario's age
y = Mercedes' age
Mario is 16 years older than Mercedes; therefore, add 16 to Mercedes' age to get Mario's age. X = Y+16 is eqn 1.
eqn 2 is X + Y = 36
Solve the two equations simultaneously. 20 is not the right age for Mercedes' age. If 20 is her age, then Mario's age is 20 + 16 = 36 and the sum of the ages is 36 + 20 = 56 but the problem says the total is 36. Thus, 20 can't be right for Mercedes' age.