You can use diary sexps (https://www.gnu.org/software/emacs/manual/html_node/emacs/Sexp-Diary-Entries.html). For example:

* TODO something Mon, Wed and Fri

  SCHEDULED: <%%(memq (calendar-day-of-week date) '(1 3 5))>

See the bottom of https://orgmode.org/manual/Deadlines-and-scheduling.html 

On Thu, Apr 5, 2018 at 12:11 AM, Cecil Westerhof <cldwesterhof@gmail.com> wrote:

I have an event that I like to repeat three times a week: on Monday, Wednesday en Friday. Do I need three entries like:
* TODO Do It
  SCHEDULED: <2018-04-06 Fri ++1w>
* TODO Do It
  SCHEDULED: <2018-04-09 Mon ++1w>
* TODO Do It
  SCHEDULED: <2018-04-11 Wed ++1w>

Or is there a better way?