Answer: Sal used a debit card and paid a total of $324.80 for the stereo. (I took the test too)
Step-by-step explanation: Multiply $21.30 by 18 months. Then subtract the interest, $58.60, from the product because Sal paid immediately with a card which implies using a debit card. You get $324.80.
Answer:

Step-by-step explanation:
First of all we need to know the relation between 1 dollar and 1 cent in order to express everything in the units required in the question.
We know that
, so the amount paid for the item with single dollars has to be multiplied by 100 to express its value in cents.

Now that we have everything in cents, we can make the subtraction:

Replacing the value in cents we get:

Answer:
d =
Step-by-step explanation:
1) To solve for d, isolate it in the equation. So, to get rid of the
with the d, add
to both sides.

Thus, d =
.
Step-by-step explanation:
