Delshad has $5 saved and she receives an allowance of $4 each week. She is able to save her entire allowance. The money Delshad has saved (y) after x weeks is given by the equation $\displaystyle{y}={4}{x}+{5}\usepackage{cmbright}\Huge\$ , which is graphed below.

She will have $21 in savings after _____ weeks.