Question 1167974
This is a standard normal distribution or Gaussian curve.

mu=5 hours
sigma=1.5 hours

z=(x-mu)/sigma
z1=(7-5)/1.5=2/1.5=4/3=1.3333 
This can be done in Excel.
P(x>7hours)=1-P(x<=7hours)=1-0.90878878=0.0913(approx)

 *[illustration Statistics]

The other two bits can be solved the same formula.

Hence proved.