THere are some rules that you need to know.

Statement 1) Because we know it is a right triangle. R should be 60 and T should be 30. There are equal lines which means equal angles. So, the angle just above X should be 60. However, it does not give us X

Statement 2) The same way. Since T is 30 then the angle just below X should be 75. However, it still does not give us X by itself.

Together) 75+60+X = 180 so, X=45

I hope I am right

But how can assume this triangle is a 30-60-90 triangle?

It could be a 45-45-90 Triangle can't it?

angle RSQ = a
angle TSU = b

so a+x+b = 180
x = 180-(a+b)

So we need value of (a+b) to determine x

statement 1 : R+2a = 180
so 2a = 180-R

Statement 2 : similarly 2b = 180-T

Combine : 2a+2b = 180*2 - (R+T) ...
we know R+T = 90 ..... right angle triangle ......

so we can find out a+b .... and x also .... No need to calculate .... its a DS question ....

Answer C.......