Answer:
x = 13
Explanation:
7x - 21 = 4x + 18
- 4x -4x
3x - 21 = 18
+ 21. + 21
3x = 39
/ 3. /3
x= 13
I'm going to be so real. I did this ages ago, so I'm not sure if this explanation is gonna be good. For alternate exterior angles, if they're equal in measure, they're parallel. Thus, we want to find when they're equal.