Amelie solves the system of equations.

D. x = 15, y = 5

Step-by-step explanation:

x + y = 20 (1)

3x - 3y = 30 (2)

From (1)

x = 20 - y

Substitute x = 20 - y into (2)

3x - 3y = 30 (2)

3(20 - y) - 3y = 30

60 - 3y - 3y = 30

- 3y - 3y = 30 - 60

-6y = -30

y = -30/-6

y = 5

Substitute y = 5 into (1)

x + y = 20 (1)

x + 5 = 20

x = 20 - 5

x = 15

x = 15, y = 5

 hope this helps :)