Question 913237
 {{{z =blue (x - 78.4)/blue(14.8)}}}
re TY: 
P(x > 55) = normalcdf(-1.5811, 100)= .9431 is the straight forward approach (not using 1-P( x  ≤  55) 
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P( x> 55)= 1 - P( z < -23.4/14.8) = 1 - normalcdf(-100, -1.5811) = 1 - .0569 = .9431  0r 94.31%
0r
P(x > 55) = normalcdf(-1.5811, 100) is the straight forward approach:
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P( x> 55) Area to the Right of z = -1.5811
the x-axis are z-scores from -5 to 5
{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, 0,exp(-x^2/2)), blue(line( -1.5811,0, -1.5811,exp(-1.5811^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z),locate(.4,-.02,.8))}}}