I am not understanding when a question states increase by → when should i place a 1+% increase and when not to.

For example

The explanation was the following :

*when you increase a number by 250%, you are NOT simply multiplying it by 2.5. Rather, you are finding*

*250% (or 2.5 times) that number and then adding it back to the original, Thus, to increase a number by 250%, you are adding 100% to 250% for a total of 350%. Therefore, multiply by 3.5*

However, in this example:

doesn’t this also mean increases by 50% so it is (0.5)(2.5)(x) rather than (0.5)(1.5)(x)?