Answer:
x = 23.4
Step-by-step explanation:

Both of this angles are same side interior angles which means both of this angles when added equal to 180 degrees
5x +15 + 3x - 3 = 180
8x - 12 = 180
+12 +12
8x = 192
x = 24
Answer: the answer is c^2 / 10
Hope this helps :p
Step-by-step explanation:
The last one is the answer