Explanation:
(ab/4) +bc = 12 -xc
multiply both sides by 4
ab + 4bc = 48 - 4xc
Transfer -4xc to the other side
ab + 4xc + 4 bc = 48
Transfer ab to the other side
4xc + 4bc = 48 - ab
take c as a common factor
c( 4x - 4b) = 48 - ab
divide both sides by ( 4x - 4b)
c ( 4x - 4b)/( 4x - 4b) = (48- ab)/( 4x - 4b)
c = ( 48-ab)/( 4x - 4b)