The answer is x = 6
Let us first define x to be the number of hours of riding lessons she can take.
X = Hours of lessons
Now, she has $200, she needs to pay $20 for grooming supplies, and the lessons cost $30 an hour. We to find the maximum amount of hours of lessons she can take, so in other words, we want to make her broke. To do this, we first convert the words into an equation:
200 - 20 - 30x = 0
Simplifying, we get
180 = 30x
x=6