Answer
$0.1271=12.71$%
Work Step by Step
Let's find the z-score for 75,000 miles:
$z=\frac{X-μ}{σ}=\frac{75000-70000}{4400}=1.14$
According to Table V, the area to the left of the standard normal curve for a z-score equal to 1.14 is 0.8729.
But, we want the area to the right (tires will last at least 75,000 miles) of the standard normal curve for a z-score equal to 1.14:
$1-0.8729=0.1271$
