Average speed is total divided by time.
Let X represent average speed;
X = 17/2 divided by 5/6. I use a method called KCF, keep the first number, change the symbol, and flip the fraction.
Then you get 17/2 * 6/5. I use the method now to cancel anything out that I Can. The denominator of 2, can be turned into a 1, and the numerator of 6, can become 3.
17/1 * 3/5, then to right it easier 17*3/1*5, then it is 51/5. Now simplify and you get:
10 1/5.
Sandy's average speed is 10/15