YMMV depending on how you do the rounding and approximate multiplication and division.
The first one can be done multiple ways. For most accurate results, increasing one number while decreasing the other is recommended. (You don't want to compute 0.3×900, for example.)
Exponential functions are written y = ab^x where a is the starting point and b is the common ratio. We know the initial worth is 52500 and each year the worth decreases 9% of the original year, making it work 91% of the previous value.
So you didn't put an actual question. To find the money he makes you just plug in the numbers. If he works 4 shifts at the theater you replace x with 4. Then, you find 85 x 4. You do the same thing with 15y.
