2x + y = 10
3x - y = 11
Solve the first for y
y = 10 - 2x
Substitute (10 - 2x) for y in the second equation:
3x - y = 11
3x - (10 - 2x) = 11 <-- distribute the
3x - 5 + x = 11
4x - 5 = 11
4x = 16
x = 4
Substitute (4) for x in
y = 10 - 2x
y = 10 - 2(4)
y = 10 - 8
y = 2
Answer: The two lines cross at (x,y) = (4,2)
Edwin
