Question 393555
a18 = a1 + 17d = 3
a52 = a1 + 51d = 173.

Subtracting the top equation from the bottom equation, we get 34d = 170 
==> d = 5. ==> a1 = -82, by substituting  d= 5 into the top equation.

==> a25 = -82 + 24*5 = 38.