7x+y=13 y=2x-0.5 elim

I'm assuming you want to solve using elimination so ...

7x + y = 13 - - - > 7x + y = 13

y = 2x - 0.5 - - - > + 2x - y = 0.5

9x = 13.5

/9 / 9

x = 1.5

y = 2x - 0.5

y = 2 (1.5) - 0.5

y = 3 - 0.5

y = 2.5

Therefore the solution to the linear system is (1.5, 2.5) or (3/2, 5/2)