3x+4y=43 find the value of y when x equals 9

To start take the equation and then plug in 9 for x

3x+4y=43

3 (9) + 4y=43

27+4y=43

Subtract 27 from each side to get all of the y's by themselves

27+4y-27=43-27

4y=16

Divide by four to get the value of one y

4y/4=16/4

y=4

4=y or y=4 because substitute x which is 9 and do the inverse all operation until y is left.