Mandy bought 3 packs of black shirts and 3 packs of yellow shirts for her tennis team. The black shirts come in packs of 5, and the yellow shirts come in packs of 2. How many shirts did Mandy buy in all? Think carefully first, then make a decision:
The number of black shirts is 3 × 5 = 15. The number of yellow shirts is 3 × 2 = 6. Mandy bought 15 + 6 = 21 shirts. So, the answer is 21.