Question

three numbers are in AP and the sum is 21 find the middle number​

Answer 1

Let the numbers be a,b, c

b=(a+c/2)

b=(21-b)/2

2b=21-b

3b=21

b=7.

Answer 2

Answer:

a=7

Step-by-step explanation:

a,a+d,a+2d

21a=3

a=21÷3

a=7