Six Digits Converter: Find the missing digits

This is a mathematical book and you must find the addition of two numbers (each one with six digits) with the given hint of four digits and the sum of the two numbers. f.e. you have the question 1 : ( - 8 5 - - - ) - ( - - 6 5 - - ) = 449046 and you have to find the answer 1 : 785633 - 336587 = 449046