How far away is west Des Moines ia from Des Moines ia?

It is no distance.

DM and WDM share a boundary, DM's 63rd Street is WDM's 1st Street.

google.com/maps?q=63rd+and+grand,+des+moines&hl=en&ll=41.582708,-93.703337&spn=0.015954,0.038409&sll=37.0625,-95.677068&sspn=34.587666,78.662109&t=h&hnear=Grand+Ave+%26+63rd+St,+Des+Moines,+Polk,+Iowa+50312&z=15">https://maps.google.com/maps?q=63rd+and+grand,+des+moines&hl=en&ll=41.582708,-93.703337&spn=0.015954,0.038409&sll=37.0625,-95.677068&sspn=34.587666,78.662109&t=h&hnear=Grand+Ave+%26+63rd+St,+Des+Moines,+Polk,+Iowa+50312&z=15

OTOH, some parts of DM are a long way from some parts of WDM.