10 blackberry plants started growing in my yard. Absent constraint, BlackBerrys will spread by 200% a month. My yard can only sustain about 50 plants. Using the logistic growth model 

b. x + 1

step-by-step explanation:

i'am smart

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