Your question doesn't say what are the options, but we can make some reasoning.
The average daily balance method is based, obviously, on the <span>average daily balance, which is the average balance for every day of the billing cycle. Therefore, in order to calculate the average daily balance, you need to sum the balance of every day and then divide it by the days of the billing cycle.
In your case:
ADB = (9</span>×2030 + 21×1450) / 30 = 1624 $
Now, in order to calculate the interest, you should first calculate the daily rate, since APR is usually defined yearly, and therefore:
rate = 0.23 ÷ 365 = 0.00063
Finally, the expression to calculate the interest could be:
interest = ADB × rate × days in the billing cycle
or else:
<span>interest = ADB × APR ÷ 365 × days in the billing cycle
In your case:
interest = 1624 </span>× 0.23 ÷ 365 × 30
= 30.70 $
Eliminate the fractions by multiplying by least common multiple.
4,9,12 all go into 36 evenly. Multiply entire equation by 36.
36/4 = 9
36/9 = 4
36/12 = 3
New equation looks like:
A has fixed one time fee of $12 and if you go to it say "m" months you pay $28 for each month, so your total cost at A is really 12 + 28m.
B has a fixed one time fee of $20 and if you go to it "m" months you pay $26 for each month, so you total cost at B is 20 + 26m.
how many months for the cost to be the same?

well, since the cost for both is the same, we can just get A's, knowing that B is the same

Answer: x = 18
explanation: the two angles are congruent bc so you can set the equation up as 9x - 40 = 5x + 32 and then solve for x
hope this helps :)