There are 3 different ways to do this, and they will produce 3 different results:
1. Row 1. K10 P4 K10
Row 2. P10 K4 P10
On the right side/outside, you'll get 2 columns of all Vs with an insert of purl bumps between them.
2. Row 1. K10 P4 K10
Row 2. K10 P4 K10
On the right side/outside, you'll get all garter stitch, but I think you'd get a faint look of 3 columns, 2 very wide with a skinny one inbetween.
3. Row 1. K10 P4 K10
Row 2. K24
I don't know what this stitch is called, but I've seen it before and it will create the 3 columns, but in a different texture.
So the question is, what result are you looking for?