Respostas

2014-07-25T00:31:45-03:00
X -> motos
y -> triciclos

x + y = 31 => x = 31 - y
2x + 3y = 70

2(31 - y) + 3y = 70
62 - 2y + 3y = 70
y = 70 - 62 = 8

x = 31 - 8 = 23 motos