Explanation
The number of cans he can fit in each row along the length of the box is 4 because \(13 \div 3=4 \frac {1}{3}\). Since \(10 \div 3= 3 \frac {1}{3}\), the number of rows he can fit along the width is 3. The total number of cans that fit is \( 4 \times 3 = 12\)