27. After Tanya changed her oil, she was able to travel $65 \mathrm{~km}$ further on a tankful of gas. This was an improvement of $8 \%$. How far was she able to drive previously

Step 1 ：The problem is asking for the distance Tanya was able to drive before she changed her oil. We know that after changing her oil, she was able to drive 65 km further, and this was an 8% improvement.

Step 2 ：We can set up the equation as follows: \(\text{previous_distance} + 0.08 * \text{previous_distance} = \text{previous_distance} + 65\)

Step 3 ：Solving this equation for \(\text{previous_distance}\) will give us the distance Tanya was able to drive before she changed her oil.

Step 4 ：\(\text{previous_distance} = \text{previous_distance}\)

Step 5 ：\(1.08*\text{previous_distance} = \text{previous_distance} + 65\)

Step 6 ：The solution to the equation gives us the distance Tanya was able to drive before she changed her oil.

Step 7 ：Final Answer: The distance Tanya was able to drive before she changed her oil is \(\boxed{812.5}\) km.