The answer is <span>4 3/4 yards of the fabric.</span>
This can be calculated using the proportion.
If the 3 1/6 yards of the fabric is enough for <span>1 1/3 shirts, how many yards are necessary of 2 shirts:
</span>

Let's express 3 1/6 as 19/6:

Similarly, 1 1/3 = 4/3:

Now, let's use this in the proportion:
<span>

</span>

Crossing the products:

⇒

⇒


⇒

Therefore, Mary needs in total 4 3/4 yards of the fabric.