We divide both sides by 5 so we can eliminate the parenthesis:
[tex]\begin{gathered} 5(y-10)=-5 \\ \frac{5(y-10)}{5}=-\frac{5}{5} \\ y-10=-1 \end{gathered}[/tex]We rearrange the terms so the terms with the unkown variable y are on the left side and the other ones on the right side:
y - 10 = -1
↓ adding 10 both sides
y - 10 + 10 = -1 + 10
y + 0 = 9
y = 9