There are three possible answers.
One solution
No solution
Many solutions
This has many solutions because if you add the like terms -10c and 8c, you’d get -2c. This makes the equation: -2c = -2c. c could equal anything and the equation would still be true because no matter what c is equal to, it’s going to be multiplied by the same number. For example, if c=2 the equation would be -4 = -4. This is true. Also, if c= -3 the equation would be 6 = 6 which is also true.
