Twice the difference of a number of 9

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?

Last week , donnell practiced the piano 3 hours longer than marcus . together, marcus and donnell practiced the piano 11 hours . for how many hours did each young man practiced the piano

Of the following, which statement or statements accurately reflect a way in which credit can be safer than cash? i. if your credit card gets stolen, you can cancel it and get your money back. ii. it is harder to lose a single credit card than a large number of bills. iii. if a merchant does not honor the agreement, you can call the credit company and dispute the charges. a. i and iii b. ii only c. iii only d. i, ii, and iii