A pottery studio gives three-hour and four-hour ceramics classes for $21 an hour. If the studio has collected $4,179 for a total of 57 classes, how many 3-hour class is and how many four-hour classes were paid for? ​

What is the common difference in the following arithmetic sequence 7,3,-1,-5

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?

Which of the following would be a reasonable estimate for the weight of a pencil? a. 1 × 10^-20 lb b. 1 × 10^20 lb c. 1 × 10^2 lb d. 1 × 10^-2 lb