Unclear: "When an equal amount is taken from equals, an equal amount results." 

This example axiom is unclear; what does taken mean?

I can see only two interpretations:
1) Subtracting equal amounts from equals produces equal amounts; then the quote should be revised to read "equal amounts result", as there are two quantities being compared
2) Subtracting equal amounts from two quantities and adding each to a third produces an amount equal to the first two; this is plainly false

So perhaps the quote should be revised.