There should be a typo in the question: the correct formula would be

Let's compute
first. We have

If we intersect this set with X, we have

So, that would be the left hand side. For the right hand side, we have

And their union is again 
Ratios equivalent to 5:1 are
10:2
15:3
we are given

Firstly , we will multiply both sides by 5

now, we can simplify it


now, we can solve for n
.............Answer
You need to multiply 25 by 8 so the answer well be 200
Whata re the answers that i can oick from