Let x = the number of raisins in each of the other 3 boxes. Then 72 + 74 + 3x = 437 raisins
Combining like terms we get 146 + 3x = 437 raisins
Subtracting 146 from both sides we get 3x = 291 raisins
Dividing both sides by 3, we get x = 291 / 3 = 97 raisins
#### 97