7.07 is the right answer to 7.07106781187 rounded to the nearest hundredth
Step 1) Add up the three given angles: 125+109+83 = 317
Step 2) Subtract the result (found in step one) from 360
360 - 317 = 43
The reason for the 360 is because for any four-sided polygon, the angles always add up to 360 degrees.
The answer is 43
Near the point (6, 6, 3), we have the approximation

where the subscripted

's refer to the corresponding partial derivatives.


So

Compare to more precise value,
4 9/20 miles haven’t been paved. You have to set the denominators of the fractions equal to each other, which would be 20. Then, subtract the numbers to get your final answer.