2.1: Three Letters

The equation $a + b = c$ could be true or false.
 If $a$ is 3, $b$ is 4, and $c$ is 5, is the equation true or false?
 Find new values of $a$, $b$, and $c$ that make the equation true.
 Find new values of $a$, $b$, and $c$ that make the equation false.

The equation $x \boldcdot y = z$ could be true or false.
 If $x$ is 3, $y$ is 4, and $z$ is 12, is the equation true or false?
 Find new values of $x$, $y$, and $z$ that make the equation true.
 Find new values of $x$, $y$, and $z$ that make the equation false.