Question 892364
This is not always true. Suppose our divisor is 10 and the two numbers are 11 and 21. Then r1, r2 = 1, 1 and r3 = 2. The divisor is not 1 + 1 - 2 = 0.


However, it is true that r1 + r2 - r3 is a multiple of the divisor.