SOLUTION:
Let us represent the amount in sales that we are to calculate with "x".
For both plans to result in the same salary, we have;
Plan 1 = Plan 2
[tex]800\text{ + 3 \% of x = 11 \% of x}[/tex][tex]\begin{gathered} 800\text{ + 0.03x = 0.11x} \\ 800\text{ = 0.11x - 0.03x} \\ 800\text{ = 0.08x} \\ \\ \frac{0.08x}{0.08}\text{ = }\frac{800}{0.08} \\ \\ x\text{ = 10,000} \end{gathered}[/tex]The amount in sales she must make in a week for both plans to result in the same salary is 10,000