21.19%
First you need to find the z-score with
X- Mean
----------- = Zscore
Standard
Deviation
Then use your z table (should be on your formula sheet if not look one up)
to find your proportion (in this problem it would be .2119) and convert it to a percent.
So plug everything in
6.64-7.2
------------ = Z-Score
.7
Z-Score= 0.8
The table showed our proportion to be .2119
therefore your percent is 21.19%