Problem:  
If you see two signs next to each other, change them to a single sign: + changes to  + changes to   changes to + 

Now there are just two signs. (For example, 35 is really +3  5) If the 2 signs are different, the answer has the sign of the larger number. (5 in this case, since 5 is larger than 3.) If they're the same, the answer also has the same sign. 

If the signs are different, subtract the two numbers. If they're the same, add. 

Final Answer: 


