Question 1170927
z=(x-mean)/sd
z < (21-20)/6 or < 1/6. That probability is 0.5662 from 2ndVARS2 normalcdf (-6, (1/6))ENTER.  Any number less than -6 may be used, I just picked that, since it is enough.

do the others the same way.

You may for the last do it two ways: Area to the left of 29 minus area to the left of 15.
The calculator would be 2nd VARS2normalcdf (15,29,20,6) ENTER
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To the right of 27 (z > (27-21)/6 or z > 1. This has area 0.1587.