To solve this, we will perform the multiplication operations first before subtracting the two results.

First, let's multiply (10.75 - 7.15) by 10.5.

10.75 - 7.15 = 3.6

3.6 * 10.5 = 37.8

Next, let's multiply (5 1/3 - 3.2) by 3 1/8.

5 1/3 - 3.2 = 2 1/6

To make the calculation easier, convert 2 1/6 to an improper fraction: 13/6

13/6 3 1/8 = 13/6 25/8 = 325/48

Now we can subtract the two results we found:

37.8 - 325/48

To subtract the decimal from the fraction, we need to first convert the decimal to a fraction:

37.8 = 37 8/10 = 378/10

Now we have:

378/10 - 325/48

To subtract these fractions, we need to find a common denominator, which is 240.

378/10 = 9072/240
325/48 = 1625/240

Subtracting these fractions gives us:

9072/240 - 1625/240 = 7447/240

Therefore, the final answer is 7447/240.