METHOD 1: (Hardest)
Do it in your head with common denominators and all that stuff but, to remember how to do that, you first need to have a 1960's flashback.
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METHOD 2: (Easier)
Start Button on your Windows tool bar.
All Programs
Accessories
Calculator
3
1/x
=
M+
4
1/x
=
M+
MR
Look in the white area for the answer
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METHOD 3: (Easiest)
Call C.P.A.
Tell him you need 1/3 and 1/4 added up and to have his people call your people with the answer.
ROTFLOL
Actually our answer is usually the same answer.
What do you want 1/3 + 1/4 to be?