Since we have that y = 10, then:
[tex]8\cdot(10)=5x-15[/tex][tex]80=5x-15\Rightarrow80+15=5x-15+15\Rightarrow95=5x+0[/tex]Then
[tex]5x=95\Rightarrow\frac{5}{5}x=\frac{95}{5}\Rightarrow x=19[/tex]In the first part, we need to sum 15 to both sides of the equation.
In the second part, we divide both sides by 5.
Then, x = 19.