We are given a capacitor with a capacitance of 25 micro-farads. To determine the lower limit we will use the tolerance of -15%, and use the following relationship:

To multiply by 15% we multiply by 15/100, like this:

Solving the operations:

Therefore, the lower limit is 21.25 micro-farads.
Now, we calculate the upper limit using the 75% tolerance, like this:

Solving the operations:

Therefore, the upper limit is 43.75 micro-farad.