Awhite dwarf is a type of remnant star that will have about the same mass as the star did, but its radius will be much smaller. a certain white dwarf has a mass of 9 times 10 superscript 30 kg and a radius of about 6600 km.

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.