Hey there!
First lets add by the number 10 on each of your sides of the problem
Like: -5x - 10 + 10
= 10 + 10
Second lets divide by a -5 because both numbers equals to that number
Like: -5x / -5 (cancel )
20/-5
x = -4
Good luck on your assessment and enjoy your day
~MeIsKaitlyn:)