Rubin need to make three german chocolate cakes. about how many cups will he need?

Can someone explain to me how to do

The party planning committee has to determine the number of tables needed for an upcoming event. if a square table can fit 8 people and a round table can fit 6 people, the equation 150 = 8x + 6y represents the number of each type of table needed for 150 people.

How do you find the distance of each number from the mean