Answer:
$17 with 10% off is the cheaper book
Step-by-step explanation:
Hello
to find the cheaper price, we need to find those prices and the compare
Step 1
20% off the original price of $19.99
by using a rule of three
if $19.99=100%
x? $ =20%
the relations are

isolating x

the discount is $3.99
the price =original price- discount
price=$19.99-3.99
price(1) = $15.995
Step 2
10% off the original price of $17
by using a rule of three
if $17=100%
x? $ =10%
the relations are

isolating x

the discount is $1.7
the price =original price- discount
price=$17-1.7
price(2) = $15.3
price(1) >price(2)
$15.995>$15.3
hence, the cheaper is the % 17 book
Have a great day.