Question 302875
6) -3x+y=7
5x+2y=3
------------
The first 5 have one equation with one of the variables in terms of the other, so the substitution is obvious.
In #6, solve eqn 1 for y, then sub into eqn 2.
6) -3x+y=7
y = 3x+7
----------
5x + 2(3x+7) = 3
5x + 6x+14 = 3
11x + 14 = 3
11x = -11
You can do the rest.