Answer:
(c) x = 1, y = -2.
Explanation:
I am not going to solve them all for you but the method of elimination is applicable to all these systems.
I'll do question c:
First, to make things easier we arrange each equation to the form ax + by = c:
y - x = -3 so
-x + y = -3..............(1)
(2x + y) / 2 = x - 1:
2x + y = 2x - 2
2x - 2x + y = -2
y = -2
Now multiply both sides by -1 so we can eliminate y by adding to equation (1):
-y = 2...................(2).
Now if we add equations (1) and (2) we eliminate y:
-x + y - y = -3 + 2
-x = -1
x = 1 is one solution.
Finally we find the value of y by substituting x = 1 in the original equation
y - x = -3
y - 1 = -3
y = -3 + 1
y = -2.