Ineed on number 18. i know the answer, it is 12.25 but i don't know how to do the work. can someone me and explain how to do the work

3.5 to the second power means 3.5 times 3.5

when you multiply. multiply as if the decimal is not there:

     3.5
x    3.5
     
       175
  + 1050

     1225

because there is a total of two decimal places after the decimal point
3.5 (one decimal place)
3.5 (one decimal place)
move the decimal point two spaces from right to left
that will put the decimal in the middle and your answer would be 12.15

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.

Ithink your answer is b