In order to calculate the cost of 7.5 lbs of walnuts, we can use the following rule of three, knowing that 3/4 lbs have a cost of $3.45:
[tex]\begin{gathered} \text{weight}\to\text{ cost} \\ \frac{3}{4}\text{ lbs}\to3.45 \\ 7.5\text{ lbs}\to x \end{gathered}[/tex]
Now, we can write the following proportion and solve for x:
[tex]\begin{gathered} \frac{\frac{3}{4}}{7.5}=\frac{3.45}{x} \\ x\cdot\frac{3}{4}=7.5\cdot3.45 \\ x=\frac{7.5\cdot3.45\cdot4}{3} \\ x=34.5 \end{gathered}[/tex]
Therefore the cost is $34.50.
