Is this a function or relation? Please explain.

What is the best approximation for the area of a circle with a radius of 4 m ? use 3.14 to approximate pi

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?

The function h (t) = -16t squared + 28t + 500 represents the height of a rock t seconds after it's propelled by a slingshot what does h (3.2) represent?