I will be heartless. Instead of moaning about your situation in long paragraphs, how have you approached this problem? Math can be hard at the earlier stages but thinking that the book is "unfair" isn't helping YOU. So, please stop with the victim mentality. Approach this rationally with the spirit of attempting and learning.

If there is a quantity 3 and it increase to 4, what is the percentage increase?

If there is a quantity 3 apples and it increases to 4 apples, how do you calculate the percentage increase of apples?

If there is a quantity 3X and it increases to 4X, what is the percentage increase?

Putting an X in the question doesn't make it algebra. The method is the same. The problem starts with identifying the initial quantity and the final quantity. The calculate the difference (as an increase or decrease). Then express that difference as a fraction of the initial quantity. Now multiply that fraction by 100 and you get the percentage increase or decrease. Whether it is numbers, apples or X, the method is the same. This is the ability you need to focus on - extracting the required information and applying the method to calculate this.