a) What proportion of the population is over 6 feet tall?

For this question I used the formula z = X - mean / standard deviation.

So, I got (X-70)/3. Then I multiplied 6 *12 to get 72 to match the inches, and then plugged it into the equation. 72-70/3= 2/3. Now, I am stuck as to what to do on how to find the proportion? Is the answer 2/3?

b) If 75 percent of the population is taller than Mike, what is Mike’s height?

I thought to use the same equation in a). So, it would be 1- 0.75= 0.25. 0.25 = (X-70)/3

So, X = 70.75. Is that the correct height?

Thanks for your time.