Answer:
b. 21
Step-by-step explanation:
The first five mutiples of 7 are: 7, 14, 21, 28, 35. You can get these by multiplying 7 to any integer.
In order to get the average of these numbers, you have to add them and divide the sum to the total number of multiples.
Let's add first.
7+14+21+28+35 = 105
Let's divided 105 by 5, which is the number of the multiples of 7.
105÷5 = 21
The answer is 21.