The ramp is the hypotenuse of a right triangle. Use the Pythagorean Theorem:

$\displaystyle{{2}}^{{2}}+{{b}}^{{2}}={{10}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{4}+{{b}}^{{2}}={100}\usepackage{cmbright}\Huge\$

$\displaystyle{{b}}^{{2}}={96}\usepackage{cmbright}\Huge\$

$\displaystyle{b}=\sqrt{{96}}\usepackage{cmbright}\Huge\$