1. **Problem 12:** Add $1 + \frac{1}{4}$. - Convert 1 to a fraction with denominator 4: $\frac{4}{4}$. - Add: $\frac{4}{4} + \frac{1}{4} = \frac{5}{4}$. - Final answer: $\frac{5}{4}$ or $1 \frac{1}{4}$. 2. **Problem 13:** Add $\frac{1}{5} + \frac{3}{5}$. - Same denominator, add numerators: $\frac{1+3}{5} = \frac{4}{5}$. - Final answer: $\frac{4}{5}$. 3. **Problem 14:** Subtract $\frac{9}{9} - \frac{8}{9}$. - Same denominator, subtract numerators: $\frac{9-8}{9} = \frac{1}{9}$. - Final answer: $\frac{1}{9}$. 4. **Problem 15:** Subtract $\frac{9}{10} - \frac{4}{10}$. - Same denominator, subtract numerators: $\frac{9-4}{10} = \frac{5}{10}$. - Simplify $\frac{5}{10} = \frac{1}{2}$. - Final answer: $\frac{1}{2}$. 5. **Problem 16:** How many $\frac{5}{8}$ inch books fit on a 20 inch shelf? - Use division: $\text{number of books} = \frac{20}{\frac{5}{8}}$. - Dividing by a fraction is multiplying by its reciprocal: $20 \times \frac{8}{5} = \frac{20 \times 8}{5} = \frac{160}{5} = 32$. - Final answer: 32 books fit on the shelf. 6. **Problem 17:** Which is greater, 5% of 90 or 90% of 5? - Calculate 5% of 90: $0.05 \times 90 = 4.5$. - Calculate 90% of 5: $0.9 \times 5 = 4.5$. - Both are equal. - Final answer: They are equal, both equal to 4.5.