To determine how many boxes of kazoos Mr. Jackson needs to order, we first need to find the total number of students in the second, third, and fourth grades. We add the number of students in each grade together:
- Second graders: 26
- Third graders: 24
- Fourth graders: 34
Total number of students = 26 + 24 + 34 = 84.
Now, let’s denote the number of kazoos in each box as \( a \).
To find the number of boxes \( b \) Mr. Jackson needs to order to ensure every student receives a kazoo, we can use the expression:
\[ b = \frac{84}{a} \]
This expression gives the total number of boxes needed, where \( 84 \) is the total number of students and \( a \) is the number of kazoos in each box.
If \( a \) does not perfectly divide \( 84 \), Mr. Jackson will need to round up to ensure every student receives a kazoo, which can be represented mathematically as:
\[ b = \lceil \frac{84}{a} \rceil \]
where \( \lceil x \rceil \) represents the smallest integer greater than or equal to \( x \).
In summary, the expression that represents the number of boxes of kazoos Mr. Jackson needs to order is \( \lceil \frac{84}{a} \rceil \).