Why does a car pushing a truck exert equal force back?

[ILoveCollege]

So i have the following question(s) in my homework assignment (This question is in regards to a car that is pushing a truck that has broken down in the middle of the road and i have to describe the motion/force):

The car is pushing on the truck, but not
hard enough to make the truck move.

Wouldn't the answer be that the car is pushing with less force than the truck is pushing back ? or would they both be equal? Because apparently the car isn't pushing with a less force than the truck and I got it wrong (my teacher won't explain to me what the right answer is and why).

The car, still pushing the truck, is at cruising
speed when the truck puts on its brakes and
causes the car to slow down

At first I thought it might be less than, but that's not the answer.

Help please ?

 

[NDbogan]

could it have something to do with work?

or the truck has a larger mass so despite how much force is exerted and there is energy is spent but there is no work seen...

 

[NDbogan]

that was for ur first quote.

as for the second half...no idea

 

[ILoveCollege]

it has something to do with the force of the car and truck. and yes the truck has a heavier mass