Answer :
[tex]5a-(8-a)=4a-10 \\
5a-8+a=4a-10 \\
6a-8=4a-10 \\
6a-4a=-10+8 \\
2a=-2 \\
a=-1[/tex]
[tex]5a-(8-a)=4a-10\ \ \ |Omit\ the\ bracket\\\\
5a-8+a=4a-10\\\\
6a-8=4a-10\ \ \ |Subtract\ 4a\\\\
2a-8=-10\ \ \ |Add\ 8\\\\
2a=-2\ \ |Divide\ by\ 2\\\\
\boxed{a=-1}[/tex]