You may have correctly substituted $\displaystyle{\left({x}-{1}\right)}\usepackage{cmbright}\Huge\$ for x to get $\displaystyle{f{{\left({x}-{1}\right)}}}={3}{\left({x}-{1}\right)}-{5}\usepackage{cmbright}\Huge\$ , but you did not simplify correctly. You should first use the distributive property and then combine like terms.