Subtract 26 from both sides:

$\displaystyle-{4}{a}+{26}-{26}\le{2}-{26}\usepackage{cmbright}\Huge\$ or $\displaystyle-{4}{a}\le-{24}\usepackage{cmbright}\Huge\$

Divide both sides by $\displaystyle-{4}\usepackage{cmbright}\Huge\$ :

$\displaystyle\frac{{-{4}{a}}}{{-{{4}}}}\ge\frac{{-{24}}}{{-{{4}}}}\usepackage{cmbright}\Huge\$ or $\displaystyle{a}\ge{6}\usepackage{cmbright}\Huge\$