Question 274441
(1) {{{3x = y - 20}}}
(2) {{{-7x - y = 40}}}
Whatever I do to one side of an equation, I must do to the other side
First, I want to subtract {{{y}}} from both sides of (1)
(1) {{{3x = y - 20}}}
{{{-y = -y}}}
(1) {{{3x - y = -20}}}
Now multiply both sides of (1) by {{{-1}}}
(1) {{{-3x + y = 20}}}
Now add (1) and (2)
(2) {{{-7x - y = 40}}}
(1) {{{-3x + y = 20}}}
{{{-10x = 60}}}
{{{x = -6}}}
Now substitute this back into (1)
(1) {{{-3x + y = 20}}}
(1) {{{-3*(-6) + y = 20}}}
{{{18 + y = 20}}}
{{{y = 2}}}
x = -6 and y = 2