As the big hand moves from 12:00 it shades the clock in. At 11:00 what is the area of the shaded region if his clock has a radius of 10 inches.

thats not a system of equations, that is a solution

inverse operation of addition

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