Multiply both sides by (4)(3) = 12:

(4)(3)

1 3

y +

(4)(3)

1 4

x = (4)(3)1

4y + 3x = 12

Subtract 4y from both sides:
4y + 3x - 4y = 12 - 4y
3x = 12 - 4y

Finally, divide both sides by 3:

3x 3

=

12 - 4y 3

x = 12 - 4y 3