mu= 1.5, sigma= .3, find : P(1.2<X<1.89)?

Answer 1

Go to your friendly z table for this. For the 1.2 minimum, this is at -one sigma. Read the cumulative probability for this can call it A.
For the 1.89 point, this is at + 1.3 sigma. Read the cumulative probability for this, call it B.
Now subtract A from B. That is your answer.

Answer 2

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