I need help on these

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

If the sales price of a dvd is $20 and the markup is 34%, what is the cost of the dvd?

Every weekday, mr. jones bikes from his home to his job. sometimes he rides along two roads, the long route that is shown by the solid lines. other times, he takes the shortcut shown by the dashed line. how many fewer kilometers does mr. jones bike when he takes the shortcut instead of the long route?