The answer is; 24/75 of the entire cake remained
If 2/5 of the initial cake was eaten, the 3/5 is what remained
MInu ate 1/3 of the 3/5 = 3/15
3/5 – 3/15 = 6/15 remained
Her brother ate; 1/5 of 6/15 = 6/75
6/15 – 6/75 = 24/75 remained
Answer:

Step-by-step explanation:
Let
x -----> Hermione was earning before the pay raise
we know that

so
The linear equation that represent this problem is

Solve for x
Divide by 1.05 both sides


So what they are saying is the sum of 2x +13=75
Therefore we can just solve for 2x, our unknown value.
2x+13=75 now subtract 13 and divide by 2 from both sides of equation to not change the equation
x+13-13=75-13
This leaves us with
x=(75-13)/2=31 therefore x=31 or our unknown value is 31.
I hope this helped. Any questions please just ask. Thank you.