Me with this question i am very confused me only on question 20

Determine the difference: 3.2 × 1010 – 1.1 × 1010. write your answer in scientific notation.

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .

Which expression is equivalent to -12(3x-3/4)