Use the distributive property on the left side:

$\displaystyle-{9}{h}+{6}\le-{7}{h}-{10}\usepackage{cmbright}\Huge\$

Subtract 6 from both sides: $\displaystyle-{9}{h}\le-{7}{h}-{16}\usepackage{cmbright}\Huge\$

Add $\displaystyle{7}{h}\usepackage{cmbright}\Huge\$ to both sides: $\displaystyle-{2}{h}\le-{16}\usepackage{cmbright}\Huge\$

Divide both sides by $\displaystyle-{2}\usepackage{cmbright}\Huge\$ : $\displaystyle{h}\ge{8}\usepackage{cmbright}\Huge\$