# Choose a useful cancellation

Calculate (8/15) × (25/12) exactly. Show a method that simplifies factors before multiplying. Explain why the same cancellation cannot be applied to (8 + 25)/(15 + 12).

**Check:** cancel 8/12 to 2/3 and 25/15 to 5/3, giving 10/9. The second expression is 33/27 = 11/9, a different value; sums are not products of those factors.