I need help on question 9 and 10 please

What does independent variable and dependent variable mean in math?

Use the quadratic function to predict f(x) if x equals 8. f(x) = 25x2 − 28x + 585

Frank has a devised a formula for his catering business that calculates the number of meatballs he needs to prepare. the formula is m=4a+2c, where c=number of children; m=number of meatballs; a=number of adults. how many meatballs are required for a party of 10 adults and 5 children?