The quotient of-54 and 9, subtracted from 8 times a number, is-18

The number is:  " -3 " .

Explanation:

Let "x" be the "unknown number" for which we are to solve.

        8x − (-54/9) = -18 ;  Solve for "x" ; 

  →  8x  − (-6) = - 18 ;

  →  8x + 6 = - 18 ;

   Subtract "6" from each side of the equation:

  →  8x + 6 − 6  =  - 18 − 6 ;

to get:   8x =  -24 ;

Divide EACH SIDE of the equation by "8" ; to isolate "x" on one side of the equation ; & to solve for "x" ; 

              8x / 8 = -24 / 8 ;

to get:   x = -3 .

The number is:  " -3 " .