How would u solve these systems?

Question

1. 2a-b=1
a+3b=4

2. Y-x=2
2x+y=8

Answer 1

2 a - 1 b = 1
2 a + 6 b = 8 (multiplied eqn 2 by 2)
-------------- subtract
-7 b = -7
b = 1
then a = 1
=================================
-1 x + 1 y = 2
+2 x + 1 y = 8
------------------subtract
-3 x = -6
x = 2
then y = 4