How can ari simplify the following expression? write the numerator and denominator with a common denominator. Then divide the numerator by the denominator. To do this, multiply the numerator by the reciprocal of the denominator. Write the numerator and denominator with a common denominator. Then divide the numerator by the denominator. To do this, multiply the numerators and multiply the denominators. Divide the numerator and the denominator by a – 3. Then divide the numerator by the denominator. Divide the numerator and the denominator by a – 3. Then simplify the numerator and simplify the denominator.