3x-y=4 2x-3y=-9 Using substitution

3x-y=4 => y=3x-4 2x-3y=-9 <=> 2x-3(3x-4)=-9 <=> 2x-9x+12=-9 -7x=-9-12 -7x=-21 => x=21/7=3 3x-y=4 <=> 3*3-y=4 9-y=4 => y=5 x=3, y=5