We have the following:
The first thing to do is calculate the area of the backyard
[tex]\begin{gathered} A=l\cdot w \\ l=68 \\ w=40\frac{1}{2} \\ \text{replacing:} \\ A=68\cdot40\frac{1}{2}=2754 \end{gathered}[/tex]Now, they tell us it is 75% of the backyard therefore
[tex]2754\cdot0.75=2065.5[/tex]Now we calculate the amount in pounds knowing that for each square foot of area 1.5 pounds are needed
[tex]2065.5\cdot\frac{1.5}{1000}=3.1[/tex]The answer is 3.1 pounds
