This is an arithmetic sequence with a common difference given by d= -7
I will start by defining my first term as u⁰=361
Now we have to think, if u⁰ is my 1st term than my 47th term would be u⁴⁶ not u⁴⁷ since i start counting from 0 and not 1.
Using the relation that describes the implicit relation of an arithmetic sequence, i can say:
u(n)=u⁰+nd where n is any number
u⁴⁶=u⁰+46d
u⁴⁶=361+46(-7)
u⁴⁶=361-322
u⁴⁶=39