Ignore the erase marks but i have no clue how to do this. asap

Since they're vertical angles, they're equal in degree measure

since they're equal, we can make the two expressions equal to each other

5a - 1 = 2a + 20
add 1 to both sides

5a = 2a + 21
subtract 2a from both sides

3a = 21
divide both sides by 3a

a = 7

now, plug the answer you found for a into one of the two expressions

5a - 1 becomes (5*7) - 1, which equals 34

to double check that they're equivalent (since they're vertical angles)

2a + 20 becomes (2*7) + 20, which equals 34

both angles are 34 degrees!