Can someone please me with this math problem?

Question

A standardized mathematics test given to 14,000 students had the scores normally distributed. The mean was 850 and the standard deviation was 75. A student scoring below 775 points was deficient in mathematics. About how many students were rated deficient?

Answer 1

850-775)/75 = 1

using the empirical rule 68% are within 1 standard deviationn from the mean

and 16% less than 1 standard deviation below the mean

16% pf 14000 = 2,240 students deficient