True or false in the body of an indirect proof you must show that the assumption leads to a contradiction

The sales tax rate is 7.25%. how much tax in dollars is added on an item that costs $56.00? a. $4.06 b. $7.25 c. $14.50 d. $60.06

Scarlet bought three pairs of sunglasses and two shirts for $81 and paula bought one pair of sunglasses and five shirts for $105 what is the cost of one pair of sunglasses and one shirt?

Billy plotted −3 4 and −1 4 on a number line to determine that −3 4 is smaller than −1 4 .is he correct? explain why or why not