Use the G A S Method
First step: Get the Given ( G )
ex: Ana has 3 apples while John has 2 oranges ( and the problem goes on and on )
Ana's 3 apples and John are the ones given.
2nd step: Look for what is Asked ( A )
How many fruits do they have in all ? 
3rd step: Give the Solution ( S )
3 + 2= 5
Just use the same method for the different kind of problems. You also have to identify the keywords in it weather you are going to add, subtract, multiply or divide. Ask your teachers or search in the internet for keywords.
It's that simple.