UPSC CDS 1 2020 Math Paper

Given:
Expression: 3x+3x+1+3x+2
Calculation:
3x+3x+1+3x+2=3x+(3x)(3)+(3x)(32)=3x(1+3+9)=3x(13)
Since, x is any natural number, we can have x=1,2,3,... so on
For x=1, we get, 3x(13)=3×13=39.
This could be the largest. But, in the options, we can see that there are numbers greater than 39 . So we check for the next natural number.
So for x=2
3x(13)=32×13=117