Answer:
x = 21
Step-by-step explanation:
2x+78 = 5x+15,
because corresponding angles will allow (2x+78) to move diagonally from 5x+15.
from built geometry knowledge,
angles diagonal from one another equal,
because (example) the angle above it would be 180-(2x+78),
then 5x+15 = 180 - [180-(2x+78)], which would ultimately be 5x+15 = 2x+78.
so, 2x+78 = 5x+15
78-15 = 5x-2x
63 = 3x
21 = x
