Will give brainliest ! show work so i can understand this

A) Convert the percentage to decimals.

40%= 0.40

Divide, 0.40/15.0

= 21.00

$21.00 dollars is the price of the book.

B) For this, we start off with finding the discounted price.

38*.25 (converted percentage)

plus 6% of the discounted price.

The book costs $28.56

For your third question:

Convert 90% to a decimal

= 0.9/40 = 36

He answered 36 questions correctly.

Hope this helps!~