Male mammals inherit an x chromosome from which of their parents? their

The answer to this question is their Mothers.

In order to become female mammals, we need to have XX chromosome, which means the mothers could give only X chromosomes
 In order to become male mammals, we need to have XY chromosomes which means the father could give either X and Y chromosomes.

For male mammals, they definitely got the Y from their fathers, so the X chromosomes definitely come from their mothers.