Ihave trouble with these questions

18.

Use the formula for the circumference of a circle.

Now enter the information you are given. You are told the circumference is 28pi, so replace C with 28pi and solve for r, the radius.

Switch the sides.

Divide both sides by 2pi.

B 14 m

19.

Look at a point on the graph. For example, when x = 4, y = 2 which is point (4, 2). x represents the number of songs. y represents the cost. The point (4, 2) means that 4 songs cost $2. Divide $2 per 4 to find a unit rate of cost of songs. $2/4 = $0.5 per song. Each song costs $0.50. If you multiply the number of songs by 0.5, you get the cost in dollars. The number of songs is x. The price of x songs is 0.50x. The price is y, so the equation is y = 0.50x.

B y = 0.50x