Question 259676
y=4x 3x+y=-21    

y-4x=0   (1)
y+3x=-21 (2)by rewriting the equation
substract (2) from (1)
Change the signs of the eq. No 2 and add the common terms

-7x=-21
-x=-21/7
-x=-7  or x=7



 2.)   y=2x-2 2x+3y=10     
y-2x=-2   (1)
3y+2x=10  (2)
Add the two equations
4y=8
so y =8/4 =2   y=2