You are tutoring a classmate in subtracting fractions. How might you summarize the rules for subtracting fractions with like denominators?

To subtract fractions, let's put a generic example.

Be the fractions

(a / b) - (c / d)

With a, b, c and d other than zero.

The subtraction of fractions is given by:

(a / b) - (c / d) = ((a * d) - (c * b)) / (b * d).

If the fractions have the same denominator then the subtraction is

(a / b) - (c / b) = (a-c) / (b)

answer

(a / b) - (c / d) = ((a * d) - (c * b)) / (b * d)

(a / b) - (c / b) = (a-c) / (b)