Insert your right needle through the first three stitches on the left needle from front to back as if to knit.
Wrap working yarn around left needle and pull it through the 3 stitches reducing them to one. Slip the new stitch to the right needle.
You have now reduced your stitches by 3 and can see where you decreased the stitches because there is now a slant. This is after working 2 rows after the decrease.