1. **State the problem:** We need to find how many students at Pierrefonds Comprehensive High School are learning to play the guitar. 2. **Given information:** - Total students = 280 - Fraction enrolled in music classes = $\frac{5}{8}$ - Fraction of music students learning guitar = $\frac{4}{7}$ 3. **Formula and approach:** - First, find the number of music students: $280 \times \frac{5}{8}$ - Then, find the number of guitar students: (number of music students) $\times \frac{4}{7}$ 4. **Calculate number of music students:** $$280 \times \frac{5}{8} = 280 \times 0.625 = 175$$ 5. **Calculate number of guitar students:** $$175 \times \frac{4}{7} = 175 \times 0.5714 = 100$$ 6. **Interpretation:** There are 100 students learning to play the guitar. **Final answer:** 100 (option a)