Question

x+7z=16
3x+y=8
y-7z=-12

Answer 1

$x = 16 - 7z \\ \ \\ \ 3(16 - 7z) = 8 \\ 48 - 21z = 8 \\ - 21z = - 40 \\ z = \frac{40}{21} \\ \\ \\ y - 7( \frac{40}{21} ) = - 12 \\ y - \frac{40}{3} = - 12 \\ y = - 12 + \frac{40}{ 3} \\ y = \frac{4}{3}$