It depends on what variable you are tying to solve for first. Say you are trying to solve for x first and then y on the first problem you wrote.
In substitution you solve one of the equations for example with 6x+2y=-10 2x+2y=-10 you solve 2x+2y=-10 for x
2x+2y=-10 -2y = -2y (what you do to one side of the = you do to the other) 2x=-10-2y (to get the variable by its self you divide the # and the variable) /2=/2 (-10/2=-5 and -2y/2= -y or -1y, they are the same either way) x=-5-y
now you put that in your original equation that you didn't solve for: 6(-5-y)+2y=-10 solve for that -30-6y+2y=-10 combine like terms -30-4y=-10 get the y alone and to do this you first get the -30 away from it +30=+30 -4y=20 divide the -4 from each side /-4=/-4 (20/-4=-5) y=-5
now the equation you previously solved for x can be solved for y. x=-5-y x=-5-(-5) a minus parenthesis negative -(- gives you a positive -5+5=0 x=0
