Standard Normal curve has mean 0 and standard deviation 1. You can use your normal curve or convert it to stand normal. Either way, the shaded region is going to be the same.

Start with the normal bell curve shape with an axis directly in the middle. That is your mean 20. The area that comes from the domain of values from x=17 to x=23 (one standard deviation away from 20) should be about 2/3's of the total area in the bell curve. The area from from x=14 to x=26 (two standard deviations away from 20) should be about 95% of the total area. Lastly, the area from x=11 to x=29 should take up 99% of the total bell curve area. Position your area accordingly between x=22 and x=27 (the right of the middle y-axis or mean)