Which situation is an example of an observational study? A. Dividing a class into thirds, giving each third a different amount of
time to read, and then testing comprehension
B. Collecting the blood pressure readings of a group of elderly
individuals in a small town
C. Testing the effectiveness of a mouthwash by allowing one group
to use it and comparing the results with those of a group that
doesn't use it
D. Having customers fill out a questionnaire about their favorite
brand of toothpaste

whatever you can spend with $11.53 or under.

step-by-step explanation:

20 - 8.47 = 11.53. take away the money he used for lunch from the starting amount of 20.

x + y = 90 5x – 10y = 90 90 – 10y = 5x 90 + 10y = 5x

step-by-step explanation:

last month maria hiked the 5-mile mountain trail a number of times and she hiked the 10-mile canal trail several times. let x represent the number of times she hiked the 5-mile trail, and let y represent the number of times she hiked the 10-mile trail. if she hiked a total of 90 miles, which equation can be used to find the number of times maria hiked each trail? x + y = 90 5x – 10y = 90 90 – 10y = 5x 90 + 10y = 5x

yes

step-by-step explanation:

yes

the answer is 8/21

hope this