The "magical" gopher isn't so magical ....
Your final solution is ALWAYS a multiple of 9.
For number sets from 10-19 it = 9
For number sets from 20-29 it =18
For number sets from 30-39 it = 27
For number sets from 40-49 it = 36
and so on....
If you take a look at the symbol chart each of those final numbers have the same symbol. If your symbol was different from their answer: you aren't able to add and subtract correctly ... back to 2nd grade for ya.
Elementary, my dear Watson!
It works on the same principle that you use to check for transpositional addition errors ... where the difference numbers add up to 9.
Any other questions class? :crazytongue: :crazytongue: :crazytongue: