x/y = 1/2, de unde y = 2x
a) x + y = 6 => x + 2x = 6 => 3x = 6 => x = 6:3 => x = 2
y = 2x = 4
b) y - x = 6 => 2x - x = 6 => x = 6
y = 2x = 12
c) x + 2y = 42 => x + 2*2x = 42 => x + 4x = 42 => 5x = 42 => x = 42/5
y = 2*42/5 = 84/5
d) 2y - 3x = 6 => 2*2x - 3x = 6 => 4x - 3x = 6 => x = 6
y = 2*6 = 12