Correct. Add 4 to all parts: $\displaystyle-{10}+{4}\le{3}{y}-{4}+{4}<{5}+{4}\usepackage{cmbright}\Huge\$

Simplify to $\displaystyle-{6}\le{3}{y}<{9}\usepackage{cmbright}\Huge\$ , then divide all parts by 3.

$\displaystyle\frac{{-{6}}}{{3}}\le\frac{{{3}{y}}}{{3}}<\frac{{9}}{{3}}\usepackage{cmbright}\Huge\$ , so $\displaystyle-{2}\le{y}<{3}\usepackage{cmbright}\Huge\$