We ignore the volume of steel and other materials.

Volume of car = V =3.3 m^3

Mass of car = m =880 kg

weight of car = 880*g N

Let the volume of displaced water = v

weight of displaced water = v*d*g=1000v*g N

For floatation of car,

weight of displaced water = weight of car

1000vg=880g

v =880/1000 =0.88 m^3

Fraction of volume immersed = v/ V =0.88/3.3= 88 /330 =0.27

fraction 0.27 of the car is immersed when it floats
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Edited.
B ) The car will sink when weight of car plus weight of water inside weighs more than weight of water displaced by the complete car inside water

Volume of water = v

Weight of water inside car= w1 =vdg=1000vg

Weight of the car (without water) = w2 =880g

weight of water displaced by the complete car inside water= W= Vdg=3.3*1000*g=3300g

w1 + w2 = W

1000vg + 880g = 3300g

1000v=2420

v=2.42 m^3

v / V =2.42/3.3=0.7333

The fraction of the interior volume when the car sinks is 0.7333

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References :

Buoyant force = Weight of water displaced
Weight of car = Volume immersed x Density of water x g

In the second part, Buoyant force should be equal to Weight of car + Weight of water inside the car

Try solving it further.

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References :