Ok this is simple. first, lets look at the 123 angle, so the entire line is 180. subtract 123 from 180 and you have 57. a triangle will always add up to 180 degress aswell. so add 58 and 57 and thats 115. so since a triangle will always add up to 180, subtract 115 from 180 and you have the missing angle:
65!
- Simplify both sides of the equation
=>x+5+4−5=x+54
=>x+5+4+−5=x+54
=>(x)+(5+4+−5)=x+54(Combine Like Terms)
=>x+4=x+54
=>x+4=x+54
- Subtract x from both sides
=>x+4−x=x+54−x
=>4=54
- Subtract 4 from both sides
=>4−4=54−4
=>0=50
Another point on the line is (6,-1)