Question 600420
a) P(120< x <180) = P( (120-160/25)< z < (180-160/25) )
                  = P( -1.6 < z < 0.8)
                  = P(z < 0.8) - P(z > 1.6)
                  = 0.7881 - (1-0.9452)
                  = 0.7881 - 0.0548
                  = 0.7333

b) P( x<120 ) = P( z < (120-160/25) ) 
              = P( z < -1.6 )
              = 1 - 0.9452
              = 0.0548

c) P( x>210 ) = P( z > (210-160/25) )
              = P( z > 2 )
              = 1 - 0.9772
              = 0.0228

Note: Used a Normal Distribution Function Table.