Question

3x + y = R$ 4,20
2x + 2y = R$ 3,60

ache o valor de x e y.

Answer 1

$3x + y = 4.20 \: \: \: \: .( - 2) \\ 2x + 2y = 3.60 \\ \\ - 6x - 2y = - 8.40 \\ 2x + 2y = 3.60 \\ \\ - 4x = - 4.80 \: \: \: \: .( - 1) \\ 4x = 4.80 \\ x = \frac{ 4.80}{4} \\ x = 1.2 \\ \\ 2x + 2y = 3.60 \\ 2 \times (1.2) + 2y= 3.60 \\ 2.40 + 2y = 3.60 \\ 2y = 3.60 - 2.40 \\ 2y = 1.20 \\ y = \frac{1.20}{2} \\ y = 0.6$
$x = 1.2 \: e \: \: y = 0.6$