Question 1009586
This is a system of equations
y = x-4
y = -x



The first equation given to you is {{{y = x-4}}}. Replace the y with -x. Why are we able to do this? Because the second equation says {{{y = -x}}}. 


So we go from {{{y = x-4}}} to {{{-x = x-4}}}


Now we isolate x


{{{-x = x-4}}}


{{{-x-x = x-4-x}}} Subtract x from both sides


{{{-2x = -4}}}


{{{(-2x)/(-2) = -4/(-2)}}} Divide both sides by -2


{{{x = 2}}}


Now we use x = 2 to find y


{{{y = -x}}}


{{{y = -2}}} Replace x with 2



So x = 2 and y = -2. They pair up to form the ordered pair or point (2,-2)


If you were to graph the two equations y = x-4 and y = -x, you'd find that they cross at the point (2,-2)