Step-by-Step Solution
**Step 1: Define the integral**
Let $I = \int_{1}^{3}\frac{\sqrt{4-x}}{\sqrt{x}+\sqrt{4-x}}dx$
**Step 2: Apply the property of definite integrals**
Using the property $\int_{a}^{b}f(x)dx = \int_{a}^{b}f(a+b-x)dx$, we have:
$I = \int_{1}^{3}\frac{\sqrt{4-(4-x)}}{\sqrt{4-x}+\sqrt{4-(4-x)}}dx = \int_{1}^{3}\frac{\sqrt{x}}{\sqrt{4-x}+\sqrt{x}}dx$
**Step 3: Add the two expressions for I**
Adding the original and transformed integrals:
$2I = \int_{1}^{3}\frac{\sqrt{4-x}}{\sqrt{x}+\sqrt{4-x}}dx + \int_{1}^{3}\frac{\sqrt{x}}{\sqrt{4-x}+\sqrt{x}}dx = \int_{1}^{3}\frac{\sqrt{4-x}+\sqrt{x}}{\sqrt{x}+\sqrt{4-x}}dx$
$2I = \int_{1}^{3}1 dx$
**Step 4: Evaluate the integral**
$2I = [x]_{1}^{3} = 3 - 1 = 2$
**Step 5: Solve for I**
$I = \frac{2}{2} = 1$