Find the critical value tc for a 90% confidence level and Sample sizes 22

Find the value of the cosine for angle a

What sums are equal to 6/12? choose all answers that are correct a.6/12+6/12+6/12+6/12+6/12+6/12 b.2/12+1/12+1/12+2/12 c.5/12+1/12 d.1/12+1/12+1/12+3/12 plz : )

Aphrase is shown read the phrase and give me the answer