Yes you are right because you understand the terms
Answer:

Let d1 be the diameter of the moon and d2 and be the diameter of the earth.Let r1 be the radius of the moon and r2 be the radius of the earth.

<h2> hope it helps you</h2>
Answer: 6.93 years
Step-by-step explanation:
Given
Rate of interest is 
Future value is given by 
For the investment to double itself, i.e. 

It takes around 6.93 years to double the investment.
Answer:
X = 35.7 Y=54.3
Step-by-step explanation:
Let the 2 angles be called X and Y were X is the smaller angle
we know that both angles are complementary therefore
X+Y=90
X = Y - 18.6 ( Given )
Y - 18.6 + Y = 90 ( substitution)
2Y = 90 + 18.6
Y = 108.6/2
Y=54.3
X= Y-18.6= 54.3-18.6 = 35.7
Check : X + Y = 35.7+54.3=90