From the image above, 5x= c ( Vertically opposite angles are equal)
To solve for the value of x that will make A parallel to B is to equate 5x to 4x+12.
Therefore, 5x= 4x+12 ( Corresponding angles are equal).
Collect like terms
5x-4x= 12
x= 12°.
Hence the value of x that will make A//B is 12°.