(I only did #1 to show you how to do substitution)
1) 2x = 1-y
5x-10y = -10
you can solve for x in the first equation and then plug it into the second equation to get a new equation in terms of y:
(2x)/2 = (1-y)/2
x = .5 - .5y
5x - 10y = -10 becomes
5(.5 - .5y) - 10y = -10
2.5 - 2.5y -...