solve each system by substitution -7x+2y=18, 6x+6y=0
2y= 7x+186x+ 3(7x+18)=06x+21x+54=027x=-54x=-26(-2)+6y=06y=12y=26(-2)+6(2)=0-12+12=0 True-7(-2)+2(2)=1814+4=18 True