An interior designer purchased 4 1/2 yards, 6 2/3 yards and 9 1/4 yards of fabric to make curtains.
how many yards of fabric did they purchase?
17 5/12 yards
19 1/2 yards
20 yards
20 5/12 yards

Add all whole numbers together 6 + 4 + 9 = 19 
Then all fractions together 1/2 + 2/3 + 1/4 = find least common denominator 12 so you get: 6/12 +8/12+3/12 = 17/12 
If the fraction has access like 17/12 convert to fraction so working back words you definitely know 12 will be on bottom so 5 has to be numerator and you left with 1 as a whole number so you get 14/12 >>>1 and 5/12 
Next you add 19 plus 1 5/12 = 20 5/12 

So the answer is the last option 20 5/12 yards.