Factorising 483 gives us 23, 7 and 3 as factors. From this we can see that 23 and (3×7) 21 are also factors.

Now by adding these 2 numbers and subtracting it with 69 gives us 25.

So the number 69 can be split into 21 + 23 + 25 which are in arithmetic progression with 2 as common difference.