To find out how thick a stack of 2 sheets is, we start with the thickness of one sheet, which is \( 1 \frac{3}{5} \) inches.
First, we convert \( 1 \frac{3}{5} \) into an improper fraction.
\[ 1 \frac{3}{5} = 1 + \frac{3}{5} = \frac{5}{5} + \frac{3}{5} = \frac{8}{5} \]
Now, we need to multiply this thickness by 2 to find the thickness of 2 sheets.
\[ 2 \times \frac{8}{5} = \frac{2 \times 8}{5} = \frac{16}{5} \]
Next, we can convert \( \frac{16}{5} \) into a mixed number. We divide 16 by 5:
\[ 16 \div 5 = 3 \quad \text{(remainder = 1)} \]
This gives us:
\[ \frac{16}{5} = 3 \frac{1}{5} \]
Thus, the thickness of the stack of 2 sheets is
\[ \boxed{3 \frac{1}{5}} \text{ inches.} \]