Hours and dollars are not the same; therefore, they cannot be expressed within the same equation. We need an equation (or inequality, rather) for just hours and then another for just money. He spends 3 hours on type x stuff and 2 hours on type y stuff, for up to 36 hours. Not more than 36, but from 0-36. So that inequality sign is less than or equal to. Now the money part. He spends $4 on x type stuff and $5 on y type stuff, but not more than $100. So that inequality sign is also less than or equal to. The 2 inequalities are
and
. Choice D.