Answer:
Step-by-step explanation:

Two planes intersect at a line. Not a point.
Answer:
0
Step-by-step explanation:
On a graph, any line that is horizontal has a slope of zero. Try any points and and plug them into the slope formula equation
(Y2-Y1/X2-X1).
The answer will always be zero.
30/18 = 10/6 = 5/3 hope this helps!