15 is less than or equal to 20+11+k over 3 less than or equal to 19

Question

15 less than or equal to 20+11+k divided by 3 less than or equal to 19.?

Answer 1

15≤(20+11+k)/3≤19,

15≤(31+k)/3≤19.

So (31+k)/3≥15, 31+k≥45, k≥14;

(31+k)/3≤19, 31+k≤57, k≤26.

So k is between 14 and 26 (inclusive): 14≤k≤26.