A box in the shape of a rectangle prism, with dimensions 12 inches by 18 inches by 12 inches, can hold exactly 12 cubes measuring 6inches on each side. If the length and width of the base are doubled, how many cubes could the new box hold 18
24
48
96

this is a direct variation proportion. y = kx

y is the total amount due, k is the constant of variation, and x is the number of texts sent.

plug in the 3.20 and the 16 to solve for the "k". this is the constant of proportionality. it is the value that will not change.

3.20 = k(16). solving you get $.20 per text.

the equation would then be y = .20x