Let's say that x is the number of days he tweets. Now, if he tweets any number of days, we can represent all of that with just x. So out expression will look like:

Hope this helps!
If you add 5x to 2x+2 you will get 7x+2. You would set this equation equal to 80, so it would be 7x+2=80. When you solve this you will get 11.1428571429, which can be rounded to 11, 11.1, or 11.14, whichever you prefer.
Expected value E(x) = 0.9994(150000 - 181) = 0.9994 x 149819 = $149,729.11