Question 43849
x+y=-7      ..1
x-y=13      ..2
rearrange equation(..2) to give:
y=x-13      ..3
now substitute equation (..3) into equation (..1) for y:
x+(x-13)=-7
2x-13=-7
2x=6
x=3         ..4
now substitute equation (..4) into equation (..3) for y:
y=3-13
y=-10

Therefore x=3 and y=-10

I hope this helps. If you have any other problems, please dont hesitate to contact me at adam.chapman@student.manchester.ac.uk