Use the definition of tangent together with the given value:

$\displaystyle{{\tan{{15}}}}^{\circ}=\frac{\text{opposite}}{\text{adjacent}}\usepackage{cmbright}\Huge\$

$\displaystyle{0.27}\approx\frac{{x}}{{7}}\usepackage{cmbright}\Huge\$

$\displaystyle{7}{\left({0.27}\right)}\approx{x}\usepackage{cmbright}\Huge\$

$\displaystyle{1.89}\approx{x}\usepackage{cmbright}\Huge\$ , which rounds off to 1.9.