Cost of Alejandro's food = $12
Tip paid by Alejandro = 20% of his bill = 20% of 12 = 2.4
Cost of Mia's food = $18
Tip paid by Mia = 15% of his bill = 15% of 18 = 2.7
Total Tip Paid = 2.4+2.7 = 5.1
Total Check Amount = 12 + 18 = 30
Total tip paid by Alejandro and Mia is r% of the total check amount.
So, we need to determine what % of 30 is equal to 5.1%
⇒ r% × 30 = 5.1
⇒ r% = 5.1 / 30
⇒ r% = 17%
Hence, r is 17%
Don't panic! The answer is 42.
But it looks like you did not copy the full question.
Let's say we placed dominoes close together such that they only fell over one way: to the right hand side. Let's call the dominoes A and B.
Domino A is to the left of domino B. If we push over domino A, then it will hit domino B to cause it to fall over as well. We have a mini chain reaction of sorts. The fall of A triggers the fall of B, but not the other way around.
For this problem, we can think of domino A as "Jillian gets a raise" and domino B as "she will buy a new car". The raise causes her to get a new car, but not vice versa.
Since we're told in the last sentence she definitely got the raise, this must mean she will definitely get the new car.
In terms of symbols, the law of detachment is stated as
- If P, then Q
- P is true
- Therefore Q is true
Side note: some books might use the term "modus ponens" instead of "law of detachment". They're the same thing.
