What is the second law of exponents

When we divide powers of the same base, this means that we have to do is subtract the exponents. ... In other words, all we would need is to divide two powers that have the same exponent then the subtraction would lead to zero

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