The degree of a line is 180, so..
Put it into an equation form: 5x + 75 = 180
1st combine like terms by subtracting 75 from 180
now your equation looks like this: 5x = 105
next you divide 5 from both sides, 105 divided by 5 is 21, so your answer is: x=21
I hope this helps!♥
