WAEC 2022 · Paper 2 · Q2

(a)
Make $y$ the subject of the relation $f = \dfrac{am}{y^3} - b$ .
(b)
The cost of 15 books is GH¢ 67.00. Some of the books cost GH¢ 5.00 each and the rest GH¢ 3.00 each. How many GH¢ 5.00 books were bought?

Worked solution (try it first)

Add $b$ to both sides: $f + b = \frac{am}{y^3}$ .
Multiply both sides by $y^3$ and divide by $(f + b)$ : $y^3 = \frac{am}{f + b}$ .
Take the cube root: $y = \sqrt[3]{\frac{am}{f + b}}$ .