Answer:
99.8 %
Step-by-step explanation:
μ  =  75     and   σ  =  5
The information about 68-95-99.7 Â rule is:
μ  ±   0,5σ       68.3 % of all values  will be in the interval
[  μ - 0,5σ  ;  μ  + 0,5σ  ]    [  72.5 : 77,5  ]
μ  ±   1σ          95 %  of all values  will be in the interval
[  μ - 1σ  ;  μ  +  1σ  ]    [  70  :  80  ]
And:
μ  ±   1,5σ        99.7 %  of all values  will be in the interval
[  μ - 1.5σ  ;  μ  +  1.5σ  ]  [ 67,5  :  82,5  ]
And still 85 is bigger than 82,5 we can conclude that approximately 99.8 % will be smaller than 85 and then "the relative frecuency of rates less than 85 is very high 99.8 %