Use a table of cumulative areas under the normal curve to fi

Use a table of cumulative areas under the normal curve to find the z-score that corresponds to the given cumulative area. If the area is not in the table, use the entry closest to the area. If the area is halfway between two entries, use the z-score halfway between the corresponding z-scores. If convenient, use technology to find the z-score. 0.047

Solution

The area left to z-score -1.68 is 0.0465 or 0.047. So required z-score is -1.68.