Question 81760
5x+4y=-2
y=4x+10 


5x+4y = -2
5x+4(4x+10) = -2
5x+16x + 40=-2
21x =-2-40
21x=-42
x=-2

y=4x+10
y=4(-2)+10
y=-8+10
y=2


Check in the other equation:
5x+4y=-2
5(-2)+4(2)=-2
-10+8=-2  It checks!!


Now, you solve your other problem just like this one!!


R^2 at SCC