Question

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

Answer 1

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)