color(white)(.....)-3x+2y =-15" "A
color(white)(.....)+2x-4y =+26" "B
Try to create additive inverses with the variables.
A xx 2: rarr color(white)(...)-6xcolor(blue)(+4y) =-30" "C
color(white)(........... ............)2xcolor(blue)(-4y) =+26" "B
C+B:color(white)(........)-4x " "= -4
color(white)(....................................)x =1
Substitute x=1 into B
color(white)(.....)+2x-4y =+26" "B
color(white)(.....)+2(1)-4y =+26
color(white)(..........)+2-4y =+26
color(white)(.................)-4y =+26-2
color(white)(.................)-4y =+24
color(white)(.........................)y =-6
Check in equation A:
-3(1) +2(-6) = -15
-3-12 = -15
color(white)(......)-15 = -15