Determine the probabilities for the following normal distribution problems.

a.= 604,= 56.8,x 635

b.= 48,= 12,x< 20

c.= 111,= 33.8,100 x< 150

d.= 264,= 10.9,250 <x< 255

e.= 37,= 4.35,x> 35

f.= 156,= 11.4,x 170

I am confused I believe I figured out question a. but after getting to the area I am not sure when do I add and when do I subtract the area? So on all of them I am confused when would I add and when would I subtract?

Thank You!