Answer :
okay so you need to get the y by itself
2x - 4y = 20
subtract the 2x over
-4y = -2x + 20
divide everything by -4
y = 1/2x - 5 <------- this is your answer
2x - 4y = 20
subtract the 2x over
-4y = -2x + 20
divide everything by -4
y = 1/2x - 5 <------- this is your answer