Let's denote the number of students in Jack's math class as \( x \).
According to the problem, Jack starts with 65 lollipops. He gives 4 lollipops to each student in his class, so the total number of lollipops he gives away is \( 4x \).
After giving away the lollipops, he has 1 lollipop left. Therefore, we can set up the following equation:
\[ 65 - 4x = 1 \]
To solve for \( x \), we can first isolate \( 4x \):
\[ 65 - 1 = 4x \] \[ 64 = 4x \]
Next, we divide both sides by 4:
\[ x = \frac{64}{4} = 16 \]
Thus, the number of students in Jack's math class is \( \boxed{16} \).