A problem with sketching lines on the graphic calculator.

I have just changed courses - from Math 10 to Math 20 - and it's hard to get used to it. The problem is the following.

The equation C=50w+300 could be used to model the cost of running the business, where w is the number of weeks and C is the cost in dollars.

The equation M=150w could be used to model the earnings, where w is the number of weeks and M is the money earned in dollars.

-On the calculator, sketch both lines so that you can clearly see where they intersect. Determine the intersection. Explain what this point means in relation to the business.

What I did was

C=M

50w+300=150w

w=3 (The intersection. The business starts making a profit after 3 weeks.)

But how do I sketch the lines?