However if something is stolen from your vehicle, that would actually be covered by your Homeowner's or Renter's insurance.

Draw an incline at an angle t to the horizontal, and a block to represent the cart.
Let m be the mass of the cart.

Draw in the following forces acting on the cart:
Its weight mg acting vertically downwards.
The reaction R of the plane on the cart, acting perpendicular to the plane and away from the plane.

You can resolve the weight mg into two components.
One is mg cos(t) and acts perpendicular to the plane in the opposite direction from R.
The other is mg sin(t) and acts parallel to the slope in the downward direction.

The cart cannot move perpendicular to the plane. There must be no net force on it in that direction. You can therefore write an equation:
R = mg cos(t)
and that gives you R directly.

Parallel to the plane, the cart can accelerate downwards. The only force in that direction is mg sin(t).
If a is the acceleration of the cart, then:
mg sin(t) = ma
(That's Force equals Mass * Acceleration)

The m cancels, leaving:
a = g sin(t).

If you are given the acceleration a, and want to know t [ this is from your earlier question ], you divide the equation by g to get:
a / g = sin(t)

That enables you to get the sine of t, and hence t.

Diagram:

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