item a)
If it have a cost of $23/4h, to calculate the value per hour we just need to do this division.
[tex]\frac{23}{4}=5.75[/tex]And this is our result. It costs 5.75 dollars per hour.
Item b)
This one is the same thing. We have a rate of 7 acre/45 pounds, for 1 pound we just do the division.
[tex]\frac{7}{45}=0.155555555\ldots\approx0.16[/tex]And this is our answer. With one pound we can plant 0.16 acres.
