The healthy weight for the dog is around 64 lbs
Answer: the player answered 30 questions correctly.
Step-by-step explanation:
Let x represent the number of questions that the player answered correctly.
Let y represent the number of questions that the player answered incorrectly.
The number of questions that the player answered is 40. It means that
x + y = 40- - - - - - - - - - -1
The score on the trivia game is obtained by subtracting the number of incorrect answers from twice the number of correct answers. If the player obtained a score of 50, It means that
2x - y = 50
y = 2x - 50
Substituting y = 2x - 50 into equation 1, it becomes
x + 2x - 50 = 40
3x - 50 = 40
3x = 40 + 50 = 90
x = 90/3
x = 30
A.

B.

Megan's solution isn't correct.
The first mistake: she subtracted 5x from the right-hand side of the equation, but added 5x to the left-hand side.
The second mistake: she divided the right-hand side of the equation by 11, but didn't divide the left-hand side.
The correct solution:
In the first 10 -> 10 - 9 = 1 (contain a 3).
In the first 100 -> 100 - 9 * 9 = 19 (contain a 3).
In the first 10^n ->
10^n - 9^n (contain a 3).
<u>The answer is 3.439 numbers contain a 3 in the first 10.000</u>