Pls help! And thank you

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

Anna is constructing a line segment that is congruent to another segment ab. for the construction, which tool should be used to mesure segment ab

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )