Explain why 2/3 can be written as 2x12 divided by 3

Average acceleration: i have no idea how to do this.

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

Tom travels between the two mile markers shown and then finds his average speed in miles per hour. select the three equations that represent this situation.