During 20 spins, a spinner landed on red 5 times. If you spin the spinner once, what is the experimental probability that it will land on red?

What number should be added to both sides of the equation to complete this square? x^2-10x=7

Having a hard time understanding this question (see attachment).

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?