I converted 13% to 0.13 but I do not know how to solve this problem.

15% of the total = 35 (by the way "of" almost always means multiply)

let t be the total

So,

.15 t = 35

divide by .15 to get t by itself

So,

35/.15 = 233.33333

Thus the total number of seals is about 233.

Bill