did i do this probability question right?

[peanut111]

Data collected over a long period of time show that the length of time x to complete a particular college entrance test is normally distributed with an average of 125 minutes and a standard deviation of 18 minutes. Ordinarily entrance tests have a time limit. What maximum time limit should be set for this entrance test if it is desired to have no more than 8% of test takers fail to finish the test during that time limit?

p(x<0.8)
x=125+z8
z=1.41
125+(1.41)8=136.28

or is this way right?
.9200 = P(Z< 1.405)= P(X< 150.2913 )

please help!

 

[tkhunny]

1) 8% is 0.08, not 0.80.

2) Make up your mind which way you are checking. p( x > a ) = 0.08 Your challenge is to find "a".