Question 1170180
<br>
x is "the number"
<br>
"The sum of a number and 9"  is  {{{ red(x + 9) }}}
<br>
"...multiplied by -2"    {{{ red(-2(x+9)) }}}
<br>
"...equals -8"    {{{ red(-2(x+9) = -8) }}}
<br>

To solve this means to isolate x on one side (then the other side is 'the number').

Divide both sides by -2:
    {{{ x+9 = 4 }}}<br>

Subtract 9 from both sides:
    {{{  highlight( x = -5 ) }}} <br>

Check:  -2(-5+9) = -2(4) = -8  (ok)