Answer:
12x - 14y cubic yards
Explanation:
a keyword in this is... difference
it also asks you to compare the first truck to the second truck not the second to the first
x = the amount of mulch the first truck can deliver
y = the amount of mulch the second truck can deliver
the first truck takes 12 trips so 12 trips multiplied by x (the amount of mulch the first truck can deliver) is 12x because it doesn't give us x
the second truck takes 14 trips so 14 trips multiplied by y (the amount of mulch the second truck can deliver) is 14y because it doesn't give us y
The question asks for the difference between the total number of cubic yards that the first truck carries through their 12 trips and the total number of cubic yards that the second truck carries through their 14 trips.
This gives us, 12x - 14y cubic yards
hopefully, this makes sense :)