Can someone solve this for me and tell me how they got the answer, because apparently every answer i out is incorrect (pic included)

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

the square root of 16 is 4.

4*4 = 16