How much of a sample remains after three half-lives have occurred?

Which is the most efficient first step to solve x in the equation 3.7x - 18 = -4.3x -34 a. add 3.7x to both sides of the equation. b. add 4.3x to both sides of the equation. c. subtract 18 from both sides of the equation. d. subtract 34 from both sides of the equation.

The variable z is directly proportional to x, and inversely proportional to y. when x is 4 and y is 13, z has the value 1.2307692307692. what is the value of z when x= 9, and y= 20

Analyze the data sets below. data set a 25,25,25,26,26,26,27,28,28,29,30,31 ,31,32,33,33,34,35,35,35 data set b 25,25,25,26,26,26,26,27,27,27,27,28 ,28,29,29,30,31,31,32,34 which of the following statement are true? select all that apply. a. data set a is relatively symmetric and data set b is skewed left. b. the means of the data sets are within 3 units from eachother. c. the data sets have the same standard deviation. d. the mean of data set a is 27.95 and the mean of data set b is 30. e. the data set b has a higher standard deviation than data set a. f. the mean and median of data set a are close in value.