X^2+y^2-4x+2y-31=0 what are the center and radius of the circle? show work

What is the value of x when x + 7 = 21?

Olive's solar powered scooter travels at a rate of 30 miles per hour. what equation can she use to calculate her distance with relation to the time she traveled? h=hours m=miles 1. h=m+30 2. m=30h 3. m=h+30 4. h=30m

Benjamin is making bow ties. how many 1/2yards lomg bow ties can he make if he has 18 feet of fabric?