Last year I made a couple of models on Desmos to demonstrate aspects of the normal distribution to my statistics students.
In this first one, you can set a normal distribution with any mean and standard deviation and then show what happens when you subtract μ and divide by σ to standardise the distribution (to do this, simply move the sliders). It’s great because students can now visualise the procedure they are carrying out.
In this one you move the sliders for ‘a’ and ‘b’ to demonstrate P(Z<a) or P(Z>b). You can hide/reveal shading for the area in question, the remaining area and any equivalent area reflected in the y-axis as and where appropriate. To hide/reveal areas, click on the circles on rows 7, 9, 10, 15, 17 or 19.
Have a play and use them how you see fit.