Mateo is constructing an equilateral triangle inscribed in a circle with center p. he draws the diameter of the circle through center p using a straight edge. next he opens his compass to a width equivalent to the radius of the circle. what is his next step?

It would have been much easier to give you the  answer which will fit your task in correct form if you had attached some options to choose the right one. Anyway, I've got the idea and I am sure this one will work and that you have almost the same in your options list. I think that his next step is to open his compass to a width equivalent to the radius of the circle. Do hope it will help you. Regards.