How do you solve this for math 7th grade 1/7-(-4/7)

The price of a visit to the dentist is calculated according to the formula 50+100n50+100n where nn is the number of cavities the dentist finds. on your last visit to the dentist, 22 cavities were found. what was the cost of your visit?

Two years ago a man was six times as old as his daughter. in 18 years he will be twice as old as his daughter. determine their present ages.

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.