Hi
You require: P( 3.70 < X < 5.81)
To find your z values use: z = (x - mean)/ standard deviation
Then, sketch a bell shaped (norm. dist or pdf) curve with mean '0' and variance '1' squared
Plot the z equivalent of 5.81 (which will be to positive therefore to the right of the '0' mean) and 3.70 (which will be negative therefore to the left of the '0' mean) extending vertical lines from each z value on the base axis up to the curve and shade the area between the two.
Using symmetry, you will discover that this is the equivalent of P(z < 5.81 z value) - (1 - P( z < than the positive 3.70 z value))
Hope this helps.
Jonty