There is a fine line between what a kindergarten kid can do and what's called *algebra*. This kind of question is it.
Basically, any addition or subtraction that you can do using the fingers of you hand is it.
Thinking "oh, great. There are some X guys, so this is algebra. I don't know that stuff!" won't get you anywhere.
Raise you hand and lift two fingers. How many more fingers do you have to raise to have three fingers?
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