All right, so let's start with a basic equation. A percent increase on a number n can be represented by n(1+x) where x is the percent increase. So if there's a percent increase of 50% on 4 objects, then it'll be 4(1+0.5) = 4(1.5) = 6.
a) Set up: 1650 = 1500x
x = 1.1. The percent of increase is 1.1 - 1 = 0.1 = 10%.
b) 1500(1.99) = 2985
These are the answers I got, but it is always helpful to double check work. Hope this helps!