Solve the equation by factoring. 5z^2-21z+4=0

Hello people, i have a math question that i need with, me, i will give the correct one brainiest, and for the other correct people, a and 5 stars.

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.

Iwill give ! if m∠a=59 and m∠3=81°, what is m∠b? m∠b= _[blank]_°