a quite difficult math problem (with multiplying and dividing big...

There is a quite difficult math problem (with multiplying and dividing big numbers) and players need to use a calculator. The tricky part is that there is a calculator, but it is missing 1 or 2 numbers. What they need to do is to go around it, adding and subtracting numbers to get the missing ones (e.g. the equation is "2345 x 987" but there is no "5". The answer is "2344 + 1″ first and then "x 987").