On a given line, (on one side) there are a total of 180°
if one line in Problem #3 is bisected by a line, with one half X and the other 120°,
do 180° (the total) minus 120° which=60°
now the hard part, that line that bisected the first line is bisecting a line that is parallel to your second line, the one with <5 and <6
this means that the big angle formed in the first one with 120° is the same angle as in the second line, leaving <5 as 120°
which means <6 is 60°, like in the top part of the problem. You're basically flipping the top line upside down, I hope it helps.
Angle CBA is the right name because it's in between C and A
Answer:

Step-by-step explanation:

Don't mind the 
Answer: 2(10+5)
Step-by-step explanation: half of 20 is 10. half of 10 is five and i put them both in parentheses. outside the parenthesis i placed 2 so it is multiplied to the inner set of numbers.
Ah clever. So you need two formulas.
1) Volume of the marble.
4(pi)r^3/3
= 4(pi)(1.4)^3/3
<span>= 11.49 (approx)
</span>
2) Formula for density.
D = M / V
= 9 / 11.49
= 0.78
0.78 < 1
Therefore the marble will float.