The expression ' one-half difference of a number cubed and one'. is written as \frac{1}{2}(x^3-1)
Well, seeing as how she mixed the clay, she has a total of 2 2/8 pounds clay (unsimplified). Although we don't know how many students she has in one class, with simple division of this number we can figure out how many student can finish the project. Removing the 2/8, we can already tell 2 students can do it, so that's a start. Now to divide the 2 pounds into 8ths. Each pound is enough for 8 students, so the 2 pounds totals to 16. Now add the extra 2 students, it's 18 total students. Hope I explained it well enough!
