Respuesta :

Substitute on the first equation: y = 3 + 2x
2x - 3(3 + 2x) = 21
2x - 9 - 6x = 21
-4x = 21 + 9
x = 30 /4
x = 7.5

Then, substitute again: y = 3 + 2•7.5 = 18