Question

How do we get to know that 30-28.5=1.5

Answer 1

3 0 . 0 0
- 2 8 . 5
--------------
0 1 . 5
since we get 1.5

Answer 2

30-28.5=1.5

30 can be written as 30.0

So,

30.0-28.5=1.5

Moreover,

30=28.5+1.5

30=30

Hence proved