1. **State the problem:** We need to find the cost of one package of white chocolate chip cookie dough (let's call it $x$) and one package of oatmeal cookie dough (let's call it $y$). 2. **Write the system of equations from the problem:** From Anjali's sales: $$1 \cdot x + 3 \cdot y = 43$$ From Molly's sales: $$2 \cdot x + 3 \cdot y = 47$$ 3. **Use the elimination method to solve for $x$ and $y$:** Subtract the first equation from the second to eliminate $y$: $$ (2x + 3y) - (1x + 3y) = 47 - 43 $$ $$ 2x + 3y - 1x - 3y = 4 $$ $$ (2x - 1x) + (3y - 3y) = 4 $$ $$ x + \cancel{3y} - \cancel{3y} = 4 $$ $$ x = 4 $$ 4. **Substitute $x=4$ back into the first equation to find $y$:** $$ 1 \cdot 4 + 3y = 43 $$ $$ 4 + 3y = 43 $$ $$ 3y = 43 - 4 $$ $$ 3y = 39 $$ $$ \cancel{3} y = \cancel{39} $$ $$ y = 13 $$ 5. **Conclusion:** The cost of one package of white chocolate chip cookie dough is $4$. The cost of one package of oatmeal cookie dough is $13$.