Given the relation R={(-2,3),(a,4),(1,9),(0,7) What value would a be to make this relation a function

How do you determine whether a relationship represented as as graph is linear or nonlinear

The amount spent on food and drink by 20 customers is shown below what is the modal amount spent ?

Match the scale and the actual area to the area of the corresponding scale drawing. scale: 1 inch to 4 feet actual area: 128 square feet scale: 1 inch to 7 feet actual area: 147 square feet scale: 1 inch to 8 feet actual area: 256 square feet scale: 1 inch to 5 feet actual area: 225 square feet area of scale drawing scale and actual area scale drawing area: 3 square inches arrowright scale drawing area: 8 square inches arrowright scale drawing area: 4 square inches arrowright scale drawing area: 9 square inches arrowright