Increase stitches evenly

I started the cable cardigan sleeve last night.
I knit in stockinette and then I needed to increase stitches evenly.
I tried to do some math.
I'm sure you know how far that got me.
Then I tried "winging it." A few stitches here, a few stitches there.
It sort of seemed to work out.
So I started setting up the cable row.
There are three separate cable patterns to set up. Written as Cable Pattern A, Cable Pattern B, Cable Pattern C. I was instructed to work Cable Pattern B, Cable Pattern A twice, then Cable Pattern C.
It was late. My brain wasn't cooperating.
So I put it down and went to bed.

This morning I tried again. I got through the first two rows. When I started the third row, my brain refused to cooperate again. And I had one extra stitch.

So I ripped out to the increase row. I started looking at the piece and wondering if there was an easy way to increase evenly - a magic knitting formula. I did a little search...

Just thought you'd like to know that this nice person appreciates that math is not my forte.

How to increase stitches evenly across a row.

Thank you, Lucia.