The product of 2 and a number x is 3/4 what is the value of x

Alrighty. Right now you have 2x = 3/4
To isolate (keep x alone on one side) you have to divide 2 from both sides.

Now you have x = 3/4 ÷ 2
Use KCP (Keep, Change, Flip)
Keep 3/4, Flip the division sign into a multiplication sign, Flip 2 into 1/2.

Now you have:

which when multiplied equals 3/8.
If you divide 3/8 you get 0.375 which is the answer.

To check your answer plug in 0.375:
2(0.375) = 3/4 and it works!

The density of the cube is 40