Please help by explaining the concepts underlying how the following problem is solved

The Wechsler Adult Intelligence Scale (WAIS) is the most common IQ test. The distribution of scores for adults taking the WAIS is approximately Normal with a mean of 100 and a standard deviation of 15. Use the 6895993 rule to answer the questions about WAIS scores. What percentage of adults score above 100'? Q 34% Q 50% Q 32% O 2.5% O 0.3% Q 68% What percentage of adults score above 145'? O 99.7% 0 99.35% 0 34% Q 16% O 0.15% O 0.3% What percentage of adults score below 85'? Q 34% O 99.1% 0 68% Q 3% O 13% O 0.3% Calling itself \"the high IQ society," MENSA requires an IQ score of 130 or higher for membership. What percentage of adults taking the WAIS test qualify for membership? (Enter your answer rounded to the nearest tenth of a percent.) Percentage: %