We can find out what LM is based on the fact that the bases of the 2 triangles are the same, this would also mean that the hypotenuse sides of the triangles should also be the same as well. Thus the sides of LM should also equal the sides of MN.
Another way, is to assume that the triangles are right angle ones, and use Pythagorean theorem to solve for the height and use that to solve for the hypotenuse.
Answer:
1117 km
Step-by-step explanation:
Because the two cities are approximately on the same North-South line, they are on the same longitude. The difference in their latitudes is 39° - 29° = 10°. We are subtracting because they are both in the northern hemisphere. The distance between them is

(10(1-(1/2)^5)/1-(1/2) =
20(1-1/32)
=155/8
The answer is 18 because 18 multiplied by 10 is 180