hi,
I have a dataset with more than 15000 data and would like to calculate the mean for only those that is bigger than and equal to 75 for all variables (x,y,z1,z2,u,v,w z1 and z2). 
my dataset is (for example) as follows :
x y z1 z2 u v w1 w2
95 83 57 50 59 39 90 48
100 92 83 82 93 92 50 50
39 40 59 68 59 49 60 89 
80 80 79 57 70 79 50 79
78 88 98 67 79 89 79 90
and so on... 
any help would be appreciated, 
big thanks in advance,
Yakamu
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