So I just did 5 * 35 as Stem, but I did it in two steps. I chose 20 for the Stem, which gave me 5 – 20 = -15 and 35 – 20 = 15. Then I did the cross addition to get 20, which I then multiplied by 20 to get 400. After that, I did -15 * 15 as Stem using 20 to get -225. So then I added 400 and -225 to get 175.
Is there an easier Stem number to use? I figured using 50 or 30 would just make things complicated too, but I didn’t try them.