This is an excersise in inverse table look up, and depends on what table you have.

Lets assume that you have a table of the cumulative standard normal, which

gives the area to the lef of z-values from 0 upwards, so these probabilities

are all greater than 0.5.

In a.) the probability is less than 0.5, so the z-score must be negative, so

we have to do an inverse look up for 1-0.2119=0.7881 then switch the sign

of the corresponding z-score. The z-score giving a p-value of 0.7881 is 0.8,

so the z-score we seek is -0.8.

RonL