HURRY! two questions here!!

what equation/formula is new/old or model/actual used for?

and what equation/formula is used for y = kx

the answers are

surface area of a cube

circumference of a circle

area of a circle

area of a triangle

area of a rectangle

volume of a rectangular prism

surface area of a rectangular prism

simple interest

direct variation (proportional relationship)

constant of proportionality (unit rate)

scale factor