Question 221313
prove that if 4x-4=3y+6 and y=2x then x=-5
by substitution y=2x so,  4x-4 = 3(2x)+6
simplified expression becomes, 4x-4=6x+6 
-4x from both sides,      4x-4x-4=6x-4x+6 equals -4=2x+6
-6 from both sides ,         -10=2x
divide both sides by 2, therefore -5=x  or x=-5