While it's pretty obvious to most of us that
-13x=90-2y
-6x=48-2y
is a system of linear equations, it'd be well to include that info plus the instructions "solve this system of linear equations."
Subtract the 2nd equation from the first:
-13x=90-2y
+6x=-48+2y
-----------------------
-7x = 42. Then x = -42/7, or x = 6.
Now subst. 6 for x in either one of the given equations. Suppose we use the 2nd equation:
-6x=48-2y
Then -6(6)=48-2y, or -36 = 48 - 2y, or 2y = 48+ 36 = 84. Then y = 42.
The solution is (6, 42).
