How do u convert 0.81 into a fraction

Taking algebra two apex courses and need with these questions

Liz is shipping a package to her friend.the maximum weight of a medium flat-rate box is 20 pounds,including the box which weighs 6 ounces.write and solve an inequality to describe the possible weight ,w, of the contents that liz will ship to her friend if she must use a medium flat-rate box.

Lana's family entered a 5-kilometer race lana's average step length is about 0.5 meter how many steps will she need to take the finish