These 2 must be used to start.
Can you clarify this statement? Do you mean you must
propose a synthesis like this:
ClPr + HC≡CEt
A + PhH
If so, it is either a ridiculous question or you don't mean 1-butyl-3-propylbenzene.
Start by drawing the product and look at the structure. For each carbon atom, or group of carbon atoms, think about which starting material each atom/group came from.
Your product has 13 carbons, and your starting materials have 3, 4 and 6.
Forget about reagents for the moment, think about how you need to clip your starting materials together to make the product. What bonds need to be formed?
Now think about how those bonds could be formed.