Question

$x - y = 1 \\ ax + y = b$
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Answer 1

x - y = 1

ax + y = b

ax + x + y - y = b + 1

x(a + 1) = b + 1

x = (b + 1)/(a + 1)

y = x - 1 = (b + 1)/(a + 1) - 1 = (b + 1 - a - 1)/(a + 1) =

= (b - a)/(a + 1)