Question. Tony has $87. He needs to buy some cheese, which costs $7 a pound and a pound of beef that costs $5 a pound. After buying the beef and his cheese, he has $61 left. How many pounds of cheese did he buy?
Answer. 3
What step-by-step reasoning justifies that answer?
Reasoning: He spent $26 because 87 - 61 = 26. He spend $21 on cheese because 26 - 5 = 21. He bought 3 pounds of cheese because 21 / 7 = 3.