We need to know the density of Marble City, hence we know the density of Pebble City.
MC density = population/area
MC density = 52,348/125
MC density = 418.784 people/miles
From the question, we know that the two cities have the same population density.
PC density = MC density
PC density = 418.784 people/miles
Use the density formula to figure out the dimension of PC
PC density = population/area
418.784 = 85,312/(l × w)
(l × w) = 85,312/418.784
11.8 w = 85,312/418.784
11.8 w = 203.7
w = 203.7/11.8
w = 17.2
The closest value of x is 17 miles
