1. Let's define the next variable,
n: number of boxes they need to sell
2. If for one pack sold they make $5.35, then for n packs they would make 5.35n dollars. The class already has $182.90 and needs a total of $750.00, then,
182.9 + 5.35n ≥ 750
3. Solving the inequality,
5.35n ≥ 750 - 182.9
5.35n ≥ 567.1
n ≥ 567.1/5.35
n ≥ 106
They must sell at least 106 boxes. The visual model of this solution is shown in the next picture: