What’s it called when you use letters in math?

Ascatterplot is produced to compare the size of a school building to the number of students at that school who play an instrument. there are 12 data points, each representing a different school. the points are widely dispersed on the scatterplot without a pattern of grouping. which statement could be true

If the dimensions of a rectangular prism are 5 ft x 3.5 ft x 2 ſt, what is the surface area?

Ineed to know the answer to this algebra question.