Martina purchased a prepaid phone card for $15.00. calls cost 5 cents a minute using this card. the credit, c (in dollars), left on the card after it is used for x minutes of calls is given by the following function.

c (x) = 15.00 -0.05x

how much credit is left on the card after martina uses it for 20 minutes of calls?

The function is
C(x) = 15.00 - 0.05x

C is how many dollars are left after
x minutes.

So if she uses it for 20 minutes, input that into the x.

C(20) = 15.00 - 0.05(20)
C(20) = 15.00 - 1
C(20) = 14.00

After 20 minutes, there are $14.00 left on the card.

Intersecting secant-tangent theorem states that if a tangent segment and a secant segment are drawn to a circle from an exterior point, then the square of the measure of the tangent segment is equal to the product of the measures of the secant segment and its external secant segment.so to break it down: 1. pq acts as the tangent and ps as the secant with an intersection at p.sr = 21rp = 3x + 3pq = 4x + 4following to equation: tangent squared = the two segments multiplied by each otherso (4x + 4) ^ 2 = (3x + 3) • (21) simplifies to 16x^2 - 31x - 47 = 0 or (16x - 47)(x + 1) x = -1 or x = 47/162. pq acts as the tangent and ps as the secant with an intersection at p (again! )sr = 16rp = xpq = 15(15) ^ 2 = 16 • x225 = 16xx = 225/163. the interesting chords are proportional to each other so a ratio is possible to set up: ap dp 10 3 + x = = —— = pc pb 8 xcross multiple to get 10x = (3 + x)(8)x = 12