Question

Three identical coins, labeled A, B, and C in the figure, lie on three corners of a square 10.0 cm on a side. Determine the x coordinate of each coin, xA, xB, and xC.

Answer 1

do you have a picture for this?
the problem is not uniquely determined with that description alone.
for example:

are two possible cases.
Note that the coordinates also depend on the position you pick to set the origin!