The amount Troy charges to mow a lawn is proportional to the time it takes him to mow the lawn. Troy charges $30 to mow a lawn that took him 1.5 hours to mow.

A. d = 20h

Step-by-step explanation:

Let the amount in dollars=d

Let the number of hours =h

Since the amount(d) Troy charges to mow the lawn is proportional to the time(h) it takes him to mow the lawn.

d=kh (k a variation constant)

Troy charges $30 to mow a lawn that took him 1.5 hours to mow.

d=$30, h=1.5 hrs

Substitution into the equation above gives:

30=k1.5

k=30/1.5=20

Substituting k=20 into the variation equation, we have:

d=20h

step-by-step explanation:

x^2 -12x + 36 + y^2 = 36

x^2 + y^2 = 12x

r^2 = 12rcos(theta)

r = 12 cos(theta)