Explanation: To understand the problem of determining how much warmer Shimla was compared to Srinagar, we need to consider the concept of temperature difference and the arithmetic operations involved with negative numbers.
The overnight low temperature in Srinagar was -17$^\circ$F, and in Shimla, it was -6$^\circ$F. To find out how much warmer Shimla was compared to Srinagar, we need to subtract the lower temperature from the higher temperature. In this case, Shimla's temperature is higher than Srinagar's, so we subtract Srinagar's temperature from Shimla's temperature.
The mathematical operation is:
\[
-6 - (-17)
\]
Subtracting a negative number is equivalent to adding the positive counterpart of that number. Therefore, the expression simplifies to:
\[
-6 + 17
\]
Performing the addition:
\[
-6 + 17 = 11
\]
Thus, Shimla was 11$^\circ$F warmer than Srinagar.
Manny's mistake was in the arithmetic operation. He subtracted -6 from -17, which is incorrect because he was trying to find the difference in warmth, not the difference in the absolute values of the temperatures. The correct approach is to subtract the lower temperature from the higher temperature, which results in a positive value indicating the degree of warmth.
In summary, the correct answer is that Shimla was 11$^\circ$F warmer than Srinagar, and Manny's calculation of -11$^\circ$F is incorrect. The key concept here is understanding how to handle subtraction with negative numbers and correctly identifying which temperature is higher to determine the warmth difference.