To convert 3 1/2 to a fraction, you would multiply the whole number, (3), by the denominator, (2), and add your sum to the numerator, (1). Your total would be 7/2. You would then follow the same steps for 9 7/8. Multiply 9 times 8 and get 72, then add 7 and your total is 79/8.
*The denominator stays the same in your final answer