Question

please explain your answer​

Answer 1

Answer:

a= 3

d=a2- a1

= 8-3

=5

an=78

an= a+(n-1)d

78=3+(n-1)×5

78=3+5n-5

78= -2+5n

78+2=5n

80=5n

n= 80÷5

n=16