6 4/5 + 6 4/5 + 2 2/3 + 2 2/3 = 18 14/15
Answer:

Step-by-step explanation:

First, we expand the equation using the distributive rule:

Hence, 
Simplify: 
Add like terms:

Subtract 13 from both sides: 
Divide both sides by -8:

Is that considered two equations?
Answer: -7=0 --> Impossible
Step-by-step explanation:
2x-7+x-11= 3x-11
2x+x-7-11=3x-11
3x-18=3x-11
3x-18+11=3x
3x-7-3x=0
-7=0
Impossible
Answer:
(5/2) ² or 25 /4
Step-by-step explanation:
x² - 5x - 18 = 0
x² -5x = 18
x² -5x + (5/2)²= 18 + (5/2)²