Beginner problem in turtle

Hello everyone

Apologies in advance if this is in the wrong thread. Please can somebody help with maybe a hint where I am going wrong please. I am new to python and currently trying to solve a problem and been stuck on it for days. The problem is to create triangles that increase by 20 and sit directly on top of each other. The top of each triangle should be exactly halfway along the baseline of the triangle above but it veers to the left or right.

Any help would be appreciated thanks

#draw triangle
from turtle import*
for shape in range(1,5):
#draw triangle
for sides in range(1,4):

#move fd to next position of next triangle
pendown ()

The arrangement I understand from your description:
draws triangles stacked on top of one another smallest on the bottom and center aligned.
You have a good start traveling up an edge of the last triangle but the distance you move over should be based on the next triangle edge length.
It has been awhile since your post. What was your solution?