Find the length of the arc intercepted by an angle of 36 in a circle with radius 12 inches

Given: ac and db are diameters. m∠3=

Can someone me with this problem . show your work .

10 ! a train starts from grand city and travels toward belleville 388 miles away. at the same time, a train starts from belleville and runs at the rate of 47 miles per hour toward grand city. they pass each other 4 hours later. find the rate of the train from grand city.