My sisters phone is dead and she needs to know his question so i'll just tell you
43789 times 9 plus 138 times 12 minus 1345 plus 124556 times 3456 minus 1287! i know this is long but she needs it to figure out a puzzle! she has to figure out the problem to the answer and that's all! i hope this is not to hard for you guys! and i need this

 I used a calculator and it said the answer is 430858661.

The only way I know how to do this sort of long sum is with a calculator
All you need to do is input 43789 * 9 + 138 * 12 - 1345 + 124556 x 3456 - 1287 and you will get the answer. Converted the words into the numerical symbols like times to *

If you want it to be more readable add commas so it's 430,858,661. You do it every 3 numbers. 

You'll want to do it the right order of operations since not all calculators do this automatically and it's a good habit >_>, using an acronym like BIDMAS (using the brit acronym lol) is a good way to remember this (Brackets, Indices, Division, Multiplication, Addition, Subtraction)

So you'll need to do the multiplication first and then the addition and then the subtraction so this is the correct order. You want to use the brackets so it does it in the right order. 
(43 789 * 9) + (138 * 12) - 1345 + (124 556 x 3456) - 1287