Question

write a system of equations with the solution (4, -3)

Answer 1

your equations are : x + y = 1 and x - y = 7

x + y = 1 --> x = 1 - y
now we have :
x - y = 7
(1 - y) - y = 7
-2y + 1 = 7
-2y = 7 - 1
-2y = 6
y = -3
now sub -3 in for y in either of the equations
x + y = 1
x - 3 = 1
x = 3 + 1
x = 4

there you go....solved by substitution