Question

My sisters phone is dead and she needs to know his question so I'll just tell you it!...

Answer 1

 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