7x - 8 = 8 + 3x
7x - 3x = 8 + 8
4x = 16
x = 16/4
x = 4
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.
Answer:
the simplified version of 3/9 would be 1/3 but other equivalent fractions of 3/9 would include but are not exclusive to: 2/6, 4/12, 5/15, and etc.
