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)