Question

How did they get 6/5?

Answer 1

x is not 6/5

Answer 2

(a,b) means all values between a and b but neither a or nor b

Answer 3

[a,b] means all values between a and b including a and b.

Answer 4

As you are aware, algebraic expression must avoid a denominator equal to zero.

The 6/5 comes from the denominator, 5x-6.
To avoid a zero denominator, we must specify the condition that 5x-6\(\ne\)0, which in turn means that 5x\(\ne\)6, or x\(\ne\)6/5, which explains from where came the 6/5.

Answer 5

Ohhh