Lines such as this have no slope. This applies to all vertical lines.
Answer: 30
Step-by-step explanation:
That is the answer
Plan A = 9 +0.17x
Plan B = 21 +0.12x
9+0.17x = 21+0.12x
X=240
9+0.17(240)=49.8
21+0.12 (240)=49.8
240 minutes and cost $49.80 each