Find the term named in the problem.

27, 37, 47, 57, ... find

a23

The first term is 27 or a1=27

the 2nd term is 37 or a2=37

notice the difference between them is 10

a2=37=a1+10

the 3rd term is 47 or a3=47

which is also a3=a1+2*10

looking at the "3" and "2"

replacing them for "n" and "n-1"

the nth term is an = a1 + (n-1) * 10

so a23=a1 + (23-1) * 10