Multiply the rational expressions and choose the correct answer. \[ \frac{x-3}{x+5} \cdot \frac{10 x+50}{7 x-21} \]

Step 1 ：Given the rational expressions \(\frac{x-3}{x+5}\) and \(\frac{10x+50}{7x-21}\)

Step 2 ：To multiply these expressions, we multiply the numerators together to get the new numerator and the denominators together to get the new denominator.

Step 3 ：The new numerator is \((x - 3)*(10*x + 50)\)

Step 4 ：The new denominator is \((x + 5)*(7*x - 21)\)

Step 5 ：After simplifying the expression, we get \(\frac{10}{7}\)

Step 6 ：Final Answer: The simplified expression after multiplying the two rational expressions is \(\boxed{\frac{10}{7}}\)