Question

Ava’s mother is 3 times as old as Ava. Her grandmother is twice as old as Ava’s mother. The sum of their three ages is 120. How old is Ava's mother?

Answer 1

let x = Ava
let y = Ava's Mother
let z = Ava's grandmother

so...
y = 3x => isolate for x => x=y/3
z = 2y

x + y + z = 120

plug them into the equation

y/3 + y + 2y =120
y/3 + 3y = 120
10y / 3 = 120
10y = (120)(3)
10y = 360
y = 360 ÷ 10
y = 36