Pre-Algebra: Chapter 9-3
Simple Probability
Probability is the chance some event will happen. It is the ratio of the number of ways an event can occur to the number of possible outcomes.
In an equation then,
Probability = number of ways a certain outcome can occur ÷ number of possible outcomes
Here’s a good overview as well.
Algebra: Chapter 10-3
Dividing Rational Expressions
To divide rational expressions, multiply the first expression by the reciprocal of the divisor.
Another way of saying it: We perform the same steps we did in Multiplying Rational Expressions – EXCEPT, before we start, we change the ÷ sign to a × sign and invert (or FLIP) the divisor (the second term).
Here again, is a link from purplemath.com