#### Answer

$x=6$ units

#### Work Step by Step

Step 1: Since the triangles are similar, their corresponding sides are in
proportion.
Step 2: This means that $\frac{3}{5}=\frac{x}{10}$.
Step 3: Solving through cross multiplication, $5x=3\times10$.
Step 4: $5x=30$
Step 5: $x=6$ units.
Check:
Step 1: Equating the two proportions to see if they reduce to the same fraction, $\frac{3}{5}=\frac{6}{10}$.
Step 2: Simplifying both sides, $\frac{3}{5}=\frac{3}{5}$.
Step 3: Therefore, the answer is accurate.