Rearrange the formula: m = 2ab/4c+b to make b the subject

m = 2ab/4c+b [times both sides by (4c+b)]

m(4c+b) = 2ab (expand the bracket)

4cm+bm = 2ab (take away bm from both sides)

4cm = 2ab - bm (take out b as the common factor)

4cm = b(2a-m) [divide both sides by (2a-m)]

4cm/(2a-m) = b