If you haven't heard this already, think of percents as "out of 100" (notice how percent has the word "cent" in it, relating to century, meaning 100). 34 percent is 34 out of 100, 90 percent is 90 out of 100, and so on. With these problems, that concept is used a bunch of times. We can model some using algebra. For example, for number 8, we can write .2x = 12, and solve for x. For numbers like 7, you simply multiply the decimal equivalent to the number given. Hope this helps, and comment with more questions.