Answer:
165
Step-by-step explanation:
1) the difference of the given sequence is:
d=397-405=389-397= -8.
2) common view of the formula of the 'n' term is:
a(n)=a(1)+d*(n-1), where n - required number of the given sequence, a(1) - the 1st term of the given sequence, d - the difference calculated above.
3) if to perform substitution (n=31; a(1)=405 and d= -8) into the formula above, then:
a(31)=405-8*(31-1)=405-240=165.
