Terry has a credit card that uses the average daily balance method. For the first 18 days of one of his billing cycles, his balance was $350

Complete question:

Terry has a credit card that uses the average daily balance method. For the first 18 days of one of his billing cycles, his balance was $350, and for the last 12 days of the billing cycle, his balance was $520. If his credit card's APR is 14%, which of these expressions could be used to calculate the amount Terry was charged in interest for the billing cycle?

(0.14/365 31)(18 $350 + 12 $520 / 31)

(0.14/365 30)(18 $350 + 12 $520 / 30)

(0.14/365 30)(12 $350 + 18 $520 / 30)

(0.14/365 31)(12 $350 + 18 $520 / 31)

(0.14/365 30)(18 $350 + 12 $520 / 30)

Step-by-step explanation:

Number of days in a year = 365

Number of days in billing cycle = (18 + 12) = 30

Interest rate per year = 14% = 0.14

Amount charged monthly :

(Monthly rate × average daily balance)

MONTHLY RATE:

(Annual interest / number of days in year) * days in billing cycle

(0.14 / 365) × 30

Average daily balance :

First 18 days ; balance = $350

Last 12 days ; balance = $520

Sum of balance / days in billing cycle

[(18 × $350) + (12 × 520)] / 30

THEREFORE, MONTHLY INTEREST CHARGE :

((0.14 / 365) × 30) ((18 × $350) + (12 × 520) / 30)

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so:

trapezoid

step-by-step explanation:

first i plotted all my points on a grid graph

i made sure all of them were in the correct quadrant

then i saw it was a trapezoid or a quadrilateral