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