Answer :
Just subtract each term from the next term.
So:
2nd term minus 1st term = 0.26 - 0.36 = -0.1
3rd term minus 2nd term = 0.16 - 0.26 = -0.1
etc
So common difference is -0.1
So:
2nd term minus 1st term = 0.26 - 0.36 = -0.1
3rd term minus 2nd term = 0.16 - 0.26 = -0.1
etc
So common difference is -0.1