Tentukan nilai x dan y pada gambar

7x = 90 + 2x.
7x - 2x = 90.
5x = 90.
x = 90/5.
x = 18.

7x + 3y = 180.
7(18) + 3y = 180.
126 + 3y = 180.
3y = 180 - 126.
3y = 54.
y = 54/3.
y = 18.