q) is true, we assume that p is true and use that to show
that q must also be true.3. This question can be rewritten as an if--then statement. If
r is a rational number, then there exists another rational number s such that r + s = 0 =
s + r. To prove that an if--then statement (p q) is true, we assume that p is true and use that to show
that q must also be true.
Proof Suppose that r is
a rational number. Hence r = a/b for some integers a and b, where b 
0.
We are trying to conclude that there exists a rational number s such that r + s = 0 = s + r. To accomplish this you need to find s (in terms of a and b).