Answer:
"If the line has a slope that is not 0, then the the line is not horizontal".
Explanation:
The contrapositive of "If p then q" is "If not q then not p".
p=a line is horizontal
not p= a line that is not horizontal
q=the line has a slope equal to zero
not q=the line has a slope that is not zero
The equivalent statement in contrapositive form is therefore:
"If the line has a slope that is not 0, then the the line is not horizontal".