I won't say how to calculate the formula, you should be able to understand it.

The final result? i8jk？ Obviously, me? It should be 1. It cannot be 0 or 2 or greater.

The result is more than 1800, so in the process of calculation? e3f？ And then what? gh？ At least one of the two numbers is greater than 900 and the other is at least 800. What about gh0? Must be bigger than e3f? So g must be 9.

For the value of e, it can't be 9. Because one digit times ten digits is at most 99×9=89 1.

So the value of e is 8?

Then let's see which two numbers can be multiplied to get a number of 880. Obviously only 98×9=882.

The result is clear at a glance, and the value of a is 9? B takes the value 8? C can only be 1? D takes the value of 9.