Please help with this, I'm stuck.

Tracy solved the following problem. which of the statements is true? 9 ÷ 3 + 6 × 2 3 + 6 × 2 9 × 2 18 her answer is correct. her answer is incorrect. she should have multiplied before dividing. her answer is incorrect. she should have multiplied before adding. her answer is incorrect. she should have added before dividing.

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

Which of the following pairs of functions are inverses of each other? o a. f(x)=x72+8 and 96-9 = 7/x+2) =8 o b. f(x)= 6(x - 2)+3 and g(x) - *#2-3 o c. $4) = 5(2)-3 and 90- 4*: 73 o d. f(x) = 6)-12 and 910 – +12