Answer:
y = 3
Step-by-step explanation:
substitute the x in 2x - y = 7 by x = 3y - 4 and then solve
2(3y - 4) - y = 7
Distribute the 2 into the parenthesis
6y - 8 -y = 7
combine like terms
5y - 8 = 7
add 8 on both sides
5y = 15
divide by 5 on both sides to isolate the y-value
y = 3