How many positive integers less than 20 have exactly 2 positive divisors?

7 numbers

2 , 3 , 5 , 7 , 11 , 13 , 17 , 19

Step-by-step explanation:

Only a prime number has exactly 2 positive divisors which are 1 and himself

and the prime numbers less than 20 are : 2 , 3 , 5 , 7 , 11 , 13 , 17 , 19

assuming you mean addition: addition and subtraction are reverse operations.

step-by-step explanation:

part 1 answer = 8

part 2 answer = 72

step-by-step explanation:

part 1 explanation = add all of the numbers, then divide by how many numbers you have. so, 200/25 = 8.

part 2 explanation = not gonna lie, this is hard to explain, so just google how to do it.