1. Which of the following equations represents a direct variation relationship between $y$ and $x$?
2. If $y$ varies directly with $x$, and $y=42$ when $x=6$, what is the constant of variation, $k$? The value of $k$ is ___.
3. The total earnings, $E$, vary directly with the number of hours worked, $h$. If a person earns 180 dollars in 12 hours, how many dollars will they earn in 15 hours? They will earn ___ dollars.
4. According to the zero exponent rule, what is the simplified value of the expression $(-50)^0$? The value is ___.
5. Simplify the expression $(7m^4n^9)^0$, assuming $m$ and $n$ are non-zero.
6. The cost of fabric, in dollars, varies directly with its length in yards. If 5 yards of fabric cost 45 dollars, 8 yards will cost ___ dollars.
7. The distance a car travels varies directly with the time it is driven. If the car travels 165 miles in 3 hours, what is the constant of variation, $k$, in miles per hour?
8. The volume of water in a pool, in gallons, varies directly with time in minutes. If the pool has 140 gallons after 4 minutes, it will take ___ minutes to fill it to 350 gallons.
9. The number of calories burned, $y$, varies directly with the number of minutes spent jogging, $x$. If a person burns 120 calories in 10 minutes, which equation represents this relationship?
10. The number of pages a student reads varies directly with the time in hours. If the student reads 75 pages in 3 hours, they will read ___ pages in 5 hours.