Question:
Let \( * \) be a binary operation on non-zero real numbers defined by:
\[ a * b = \frac{ab}{5} \]
Find \( x \) if:
\[ 2 * (x * 5) = 10 \]
Solution:
Step 1: Compute inner operation
\[ x * 5 = \frac{x \cdot 5}{5} = x \]
Step 2: Substitute into equation
\[ 2 * x = 10 \]
Step 3: Apply operation definition
\[ 2 * x = \frac{2x}{5} \]
So,
\[ \frac{2x}{5} = 10 \]
Step 4: Solve for \( x \)
\[ 2x = 50 \Rightarrow x = 25 \]
Final Answer:
\[ \boxed{25} \]