Final answer:
The equation that can be used to find the regular price of a museum ticket when the sale price is 90% of the regular price is 54 = 0.9r. The regular price can be calculated by dividing 54 by 0.9, which gives a result of $60.
Step-by-step explanation:
To find the regular price, r, of a museum ticket when the sale price is 90% of the regular price, you can use the equation 54 = 0.9r.
To solve for r, divide both sides of the equation by 0.9. This gives us:
r = 54 / 0.9
Now we can calculate:
r = 60
So, the regular price of the museum ticket is $60.