Answer:
The discount is $0.8d.
Step-by-step explanation:
Given that,
The original cost of Tamara's purchase is d dollars.
Tamara uses a coupon to save 20% off her purchase at the bookstore.
Discount = 20%
Discount is applied to the original cost.
Discount = d-(20/100)d
Discount = 0.8 d
Hence, the discount is $0.8d.
Actually, the answer is not A, if you're saying A is the first choice above. That's incorrect. You will need to use the Geometric mean for right triangles here to figure out what the value of a is. We will use this form:

. We have a value for YZ of 3; side a is XZ. That means in order to solve this we need WZ, which we can find using pythagorean's theorem. 3^2 + 4^2 = c^2 and 9 + 16 = c^2 and c = 5. Now we fill in accordingly:

. Cross-multiply to get 3XZ=25 and side XZ is

. XZ is 25/3 and YZ is 3, so 25/3 - 3 = XY. That means that XY (side a) = 16/3 or 5 1/3, choice B, or the second one down.
Answer:
The order of operations
Step-by-step explanation:
you should do what is possible within parentheses first, then exponents, then multiplication and division (from left to right), and then addition and subtraction (from left to right). (Assuming your talking about algebra)