1. **Problem a:** 3 cups cost 7 in total. We want to find the cost of 15 cups. 2. Use the unit cost formula: cost per cup = total cost / number of cups. 3. Calculate unit cost: $$\frac{7}{3} = \frac{7}{3}$$ per cup. 4. Multiply unit cost by 15 cups: $$15 \times \frac{7}{3} = 15 \times \frac{7}{3} = 5 \times 7 = 35$$. 5. So, 15 cups cost 35. 6. **Problem b:** 4 glasses cost 24 in total. Find the cost of 7 glasses. 7. Calculate unit cost: $$\frac{24}{4} = 6$$ per glass. 8. Multiply unit cost by 7 glasses: $$7 \times 6 = 42$$. 9. So, 7 glasses cost 42. 10. **Problem c:** Find the difference between the median and mode of the numbers 18, 1, 3, 18, 28, 4. 11. Sort the numbers: 1, 3, 4, 18, 18, 28. 12. Median (middle value) for even count is average of middle two: $$\frac{4 + 18}{2} = \frac{22}{2} = 11$$. 13. Mode (most frequent number) is 18 (appears twice). 14. Difference = median - mode = $$11 - 18 = -7$$. **Final answers:** - 15 cups cost 35. - 7 glasses cost 42. - Difference between median and mode is -7.