So, the one you picked is correct because:
[tex]2^{a-3} = b-4[/tex]
[tex]log_2(b-4) = a-3[/tex]
[tex]log_2(b-4) +3 = a[/tex]
This eliminates the second option because there is only 1 possible value for a.
The 4th option is also correct because it's saying:
[tex]log_2(b-4) = a-3[/tex]
Now, just by pure logic, you can tell that to solve for b, you have to use option 3 because Option 5 has already been used to solve for a.
So, your answers are: #1, #3, and #4.
