Explanation

When we use (pen) to write, we use (ink) instead of (pen). Then we have to use the preposition (in) but not ( with). Eg. I write in ink.

When we use pencil, we have to use (with) but not (in). Eg. I wrote with a pencil.

I write in ink. Or I write with a pencil.

 Sh6-8-2023