Answer:
20
Step-by-step explanation:
We can group the known and unknown values to each other. So we can say that the whole angle, which is 180 degrees, is made of 100 degrees and 4x. This means that 100 + 4x = 180. This also means that 4x = 180 - 100 = 80. Since 4x = 80 we can divide 80 by 4 and get the answer of 80 / 4 = 20
