Answer:
3.93701 inches
Step-by-step explanation:
To be honest, I just looked up centimeters to inches and plugged 10 in.
5.
Let x be the age of the father and y be the age of the son. As of today, he's 3 times older, so we have 
10 years ago their ages were, respectively, x-10 and y-10, and the father was 5 times older: 
So, we have the system

Using the first equation, we can substitute every occurrence of "x" with "3y" in the second equation:

So, the son is 20 years old, which means that the father is 60 years old.
Indeed, 10 years ago they were 10 and 50 years old, so the father was 5 times older.
6.
Let x be the age of the grandfather and y the age of the granddaughter. We know that the grandfather is 10 times older: 
He also is 54 years older: 
Again, if we substitute x=10y in the second equation we have

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If we set the vertex at (0,0) then the curve goes through (30,30)
<span>y = 1/30 x^2 </span>
<span>x^2 = 30y </span>
<span>Since the parabola x^2 = 4py has its focus at y=p, 4p=30 and the mic should be 15/2 inches up from the vertex.</span>
What’s the question though lol
The Answer is x=2 for this problem