The system of equations is
[tex] \left \{ {{y=1000+0.25x} \atop {y=2000+0.10x}} \right. [/tex]
Dawn earns $1000, and we add to that the commission she makes, 25% of her sales. 25%=25/100=0.25, so we have 1000+0.25x.
Claire earns $2000, and we add to that the commission she makes, 10% of her sales. 10%=10/100=0.10, so we have 2000+0.10x.