Explanation:

- Start with an original number, say $x$.

- Increase $x$ by 25%: $x+0.25x=1.25x$.

- Decrease this result by 10%: $1.25x-0.10\times 1.25x$.

- Simplify to $1.25x\times 0.90=1.125x$.

- Given $1.125x=72$.

- Solve for $x$: $x=\frac{72}{1.125}=64$.

- Option 1: 75

- If 75, $1.25\times 75=93.75$.

- Decreasing by 10% gives 84.375, not 72.

- Option 2: 84

- If 84, $1.25\times 84=105$.

- Decreasing by 10% gives 94.5, not 72.

- Option 3: 64

- If 64, $1.25\times 64=80$.

- Decreasing by 10% gives 72, which matches.

- Option 4: 56

- If 56, $1.25\times 56=70$.

- Decreasing by 10% gives 63, not 72.

The correct answer is:

- Option 3: 64