-1,4
you use the rule (x,y) to (x-3,y)
1 + 4x = -5 + 7x
<u> -4x </u> <u> - 4x </u>
1 = -5 + 3x
<u>+5 </u> <u>+5 </u>
6 = 3x

2 = x
Answer: x = 2
Answer:12300
Step-by-step explanation:12.3x1000
1/4 * 1/3 * 1/2 * 1/1 = 1/24 chance that all 4 letters are placed in the correct envelopes.
With the first envelope, there are 4 choices of letters, so the probability of picking the correct letter is 1/4.
With the second envelope, there are 3 remaining letters, so the probability of picking the correct letter is 1/3.
The same logic follows the the third and final letter.