Normally 7 envelopes but on rare occasions, there may be more due to If the packages are filled with Envelopes. Also depending on if the 7 packages are boxes of envelopes, and in that case, 140 envelopes times 7, which would be 980 envelopes in the 7 packages. 140 * 7 = 980.
Number 4 is C... 21
To complete the question, make the equation 5x + 15 + 3x - 3 = 180 because of supplementery angles.
Just solve for x to get 21.
Number 5 is C... 120
To complete this question, sub 21 in for X in the equation 3x - 3 to get 60. Subtract 60 from 180 to get 120.