Answer:
1. x/4
2. 2/3+x
3. 9-n
Step-by-step explanation:
1. "A number" is an unknown value, so we set that as the variable. When a number is being divided, it's the divisor in a division problem (the first number)
2. The "sum" is the answer to an addition problem (like how the "quotient" is the answer to a division problem), which is why we know to add. Again, "a number" is the unknown value so we set that as the variable.
3. Because Drew is "n" years younger than Joe, Joe's age - n = Drew's age. The question tells us that Joe is 9 years old, so the expression would be 9-n.
I hope this helps! If it does, a brainliest would be much appreciated :)