Start with your explicit formula which I have provided for you below.

In the formula, the <em>n </em>represents what term we want to find.
Since we want to find the 52nd term, we plug 52 in for <em>n</em>.
Then,
represents our first term in the sequence which is -3.
Now, <em>d</em> is the difference between each of the terms and it's 15.
So we have
.
Now just simplify from here.
First, apply order of operations (inside parentheses first).
.
Now, multiply before we add.
.
Now just add to get
.