Simple...
you have: -5x-4(5x-15)=165
You want to solve for x.
To do so, you must isolate the variable...
-5x-4(5x-15)=165
1.)Combine like terms/Simplify terms.
-5x-20x+60=165
-->>
-25x+60=165
Now just simplify...
-25x+60=165
-60 -60
-25x=105
[tex] \frac{-25x}{-25} = \frac{105}{-25} [/tex]
x=[tex] -\frac{21}{5} [/tex]
Thus, your answer.
