Question

Let x be the age of Joey and y be the age of Maria today, then y = 6x and y + 20 = 2(x + 20)

Subsitute y = 6x into y + 20 = 2(x + 20)
6x + 20 = 2x + 40
4x = 20
x = 5
and y = 6(5) = 30
Therefore, the age of Joey and Maria are 5 and 30 respectively

let Joey's age be a
6a + 20 = 2(a + 20)
6a + 20 = 2a + 40
4a = 20
a = 5

so Joey's age is equal to 5 and Maria's age is equal to 30.