Solve the following compound inequality and answer the questions that follow:
−15≤6−3(2x−5)<9
a. (i) Solve the compound inequality step by step, carefully indicating where (if at all) the direction of an inequality sign changes.
b. (ii) Write the solution set first in set-builder form and then in interval notation.
c. (iii) Show, by direct substitution of two suitable test values, that your final solution satisfies the original compound inequality.