a=3+cb\displaystyle a = \frac{3 + c}{b}a=b3+c
Make b b\,b the subject of the formula.
Practise CIE IGCSE Maths Changing the Subject of a Formula with exam-style questions for Core and Extended tier. 20 questions, matched to the CIE IGCSE Maths (0580) specification and written in Paper 1 and Paper 3 (Core) or Paper 2 and Paper 4 (Extended) style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.