TI-83 or TI-84 will do these for you, without the need of a
table or calculating the z-score.

Here's how you put it in:

The lower value is 50 and the upper value is 70, μ = 40; σ = 16

normalcdf(lower,upper,μ,σ)

Your problem:

normalcdf(50,70,40,16)

Press ENTER

Read the answer 0.2355891706

Round off like you were told.

Edwin