Question

which of euclids axioms demonstrates the statement that if $x + y = 10$, then $x + y+z = 10 + z$?
a first axiom
b second axiom
c third axiom
d fifth axiom

Explanation:

Euclid's second axiom states that if equals be added to equals, the wholes are equal. Here, since $x + y$ and $10$ are equal, adding $z$ to both sides results in equal sums, which is in line with the second - axiom.

Answer:

b. Second Axiom