Answer is 21.4 %
Used a probability tree diagram.
Answer:
mass - 1395.28 g
Step-by-step explanation:
density = mass / volume
65.2 g/cm^3 = mass / 21.4 cm^3
65.2 g * 21.4 = mass (cm^3 cancels out)
1395.28 g = mass
You set the expressions equal to each other since they are congruent, then solve.
5x + 24 = 9x - 17
First subtract 24 from both sides to get
5x = 9x - 41
The subtract 9x from both sides to get
-4x = -41
Then divide both sides by -4 to get
x = 41/4 or as a decimal x = 10.25
Arccos is the same thing as inverse cosine which is used when you are looking for an angle measure. Make sure your calculator is in degree mode. Hit 2nd button then cos and you will see this on your screen:

and it is following the parenthesis there that you will enter your decimal. The inverse cosine of .67 is an angle measure of 47.93°