The amount of money the students have raised so far is $\displaystyle{2200}\cdot\frac{{3}}{{5}}=\frac{{6600}}{{5}}=\text{\$}{1320}\usepackage{cmbright}\Huge\$ . They still need to raise $\displaystyle\text{\$}{2200}-\text{\$}{1320}=\text{\$}{880}\usepackage{cmbright}\Huge\$ .