Because a prime number has to be greater than 1.
Answer:

Step-by-step explanation:
For this you just have to make an equation and in order to do that you have to know that all these angles will equal 180°. Now we can write it out.

Now we combine like terms:

Add the 9 on both sides:

Divide the 21 on both sides:

Answer:
vrtOne example is the equation:
2x + 6 = 4x/2 + 12/2
To solve this, we need to transpose like terms to the same side.
2x - 4x/2 = 12/2 - 6
2x - 2x = 6 - 6
0 = 0
Since both sides are zero, it means that the equation has infinite number of solutions.
Step-by-step explanation: