1. **Stating the problem:** (a) Find the number $x$ such that 75% of $x$ is 36. 2. **Formula and explanation:** We use the formula for percentage: $$\text{Percentage} \times \text{Number} = \text{Part}\implies \frac{75}{100} \times x = 36$$ 3. **Solve for $x$:** $$\frac{75}{100} x = 36$$ Divide both sides by $\frac{75}{100}$: $$x = \frac{36}{\frac{75}{100}}$$ Rewrite division as multiplication by reciprocal: $$x = 36 \times \frac{100}{75}$$ Simplify the fraction $\frac{100}{75}$: $$x = 36 \times \frac{\cancel{100}}{\cancel{75}} = 36 \times \frac{4}{3}$$ Multiply: $$x = 36 \times \frac{4}{3} = \frac{36 \times 4}{3} = \frac{144}{3} = 48$$ 4. **Answer:** The number is $\boxed{48}$. 5. **Stating the problem:** (b) What percent of 40 is 18? 6. **Formula and explanation:** Let the percent be $p$. $$p \times 40 = 18$$ Express $p$ as a decimal fraction: $$\frac{p}{100} \times 40 = 18$$ 7. **Solve for $p$:** $$\frac{p}{100} = \frac{18}{40}$$ Multiply both sides by 100: $$p = 100 \times \frac{18}{40}$$ Simplify the fraction $\frac{18}{40}$: $$p = 100 \times \frac{\cancel{18}}{\cancel{40}} = 100 \times \frac{9}{20}$$ Multiply: $$p = \frac{100 \times 9}{20} = \frac{900}{20} = 45$$ 8. **Answer:** 18 is 45% of 40.