Answer: The required quantity of the extra fabric that will be left after making the skirt is 1.5 yards.
Step-by-step explanation: Given that Kate has 
 yards of fabric and needs
 yards of fabric and needs 
 yards to make a skirt.
 yards to make a skirt.
We are to find the quantity of the extra fabric that will be left after making the skirt.
According to the given information, we have

and

Therefore, the quantity of the extra fabric that will be left after making the skirt is given by

Thus, the required quantity of the extra fabric that will be left after making the skirt is 1.5 yards.