How are parentheses used when grouping factors

Which speed is the fastest (use 1 mile ≈ 1.6 kilometers)? a. 12 miles/hour b. 18 feet/second c. 19 kilometers/hour d. cannot be determined

The box plot shows the number of raisins found in sample boxes from brand c and from brand d. each box weighs the same. what could you infer by comparing the range of the data for each brand? a) a box of raisins from either brand has about 28 raisins. b) the number of raisins in boxes from brand c varies more than boxes from brand d. c) the number of raisins in boxes from brand d varies more than boxes from brand c. d) the number of raisins in boxes from either brand varies about the same.

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.