Dina is twice as old as Andrea. The sum of their age is 72. Find their present ages.

Dina is twice as old as Andrea. The sum of their age is 72. Find their present ages.

Let d be Dina's age. Let a be Andrea's age. We're given:

1. d = 2a <-- Twice means multiply by 2
2. a + d = 72

Substitute equation (1) into equation (2):
a + 2a = 72

Type this equation into our search engine and we get:
a = 24

Substitute a = 24 into equation (1):
d = 2(24)
d = 48

So Andrea is 24 years old and Dina is 48 years old