Step-by-step explanation:

an=a+n-1*d

78=3+5n-5

80=5n

n=16

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Answer:

Hey!

Here is your answer...

16th term of the AP: 3,8,13,....... is 78.

Step-by-step explanation:

a= 3

d= a2-a1

= 8-3

= 5

an= a + (n-1) d

78= 3 + (n-1) 5

78= 3+ 5n-5

78= -2+5n

78+2= 5n

5n= 80

n= 80/5

=16.

Hope! it will help you...