EXPLANATION
We can apply the Secan Secant Theorem in order to get the value of the side JF as shown as follows:

Replacing terms:

Adding numbers:

Dividing both sides by 40:

Multiplying numbers and simplifying:

As ground to J is the sum of JF + F to ground, we can isolate the measure of the segment JF as shown as follows:

The answer is 60.6 feet