First you need to find a common denominator which in this case would be 12 on the bottom for all three fractions. the 1/3 gets changed to 4/12 because it is multiplied by 4. Do the same with the other one to get 4/12 + 4/12 = 8/12. Next you need to multiply 3/4 by 3 to get the common denominator 9/12. Lastly you subtract 9/12 - 8/12 = 1/12 meters of ribbon. Hope this helps :)
