Hello!
The answer is:
The number of teeth of Gear 2 is 90 teeth.

Why?
To calculate the number of teeth for the Gear 2, we need to use the following formula that establishes a relation between the number of RPM and the number of teeth of two or more gears.

Where,
N, are the rpm of the gears
Z, are the teeth of the gears.
We are given the following information:

Then, substituting and calculating we have:




Hence, we have that the number of teeth of Gear 2 is 90 teeth.
Have a nice day!