Pe ling needs 2 yard of fabric for a craft project. she has 3 feet already. how many inches of fabric does she still need ?

First, you want them to be the same units. 
We'll convert yards to feet.

Since there are 3 feet in a yard 

2 yards * 3 = 6 feet

So she needs 6 yards and has 3 feet.

6-3=3     3 feet is needed

So to make things easier convert 3 feet to inches
12 in. in a foot

12*3 feet= 36 inches
She needs 36 inches of fabric

She needs 2 yards. 

2 yards = 6 feet

3 feet = 36 inches

So, she has half of it done already.
If 2 yard = 6ft, then 1 yard = 3ft.
In 1 foot, there is 12in.

Therefore, she still needs 36 inches of fabric.