ANSWER
Find out the how old was we when he died.
To proof
Let us assume that the age of the Adam be x
As given
Adam lived a quarter of his life as a boy as fifth as a young man, a third in middle-age and 13 years in retirement.

L.C.M of denominator i.e ( 4,5,3) =60
than the equation becomes
60x = 15x + 12x +20x +780
60x - 47x = 780
13x = 780

x = 60 years
therefore the Adam age when he died is 60 years.
Hence proved
Answer:
Any value of x x makes the equation true. All real numbers Interval Notation: ( − ∞ , ∞ )
.
As usual, draw a diagram. You can easily see that if you are x away from the wall,
<span>the angle of elevation of the bottom of the screen (A) is </span>
<span>cotA = x/3 </span>
<span>A = arccot(x/3) </span>
<span>angle B to the top is </span>
<span>cotB = x/10 </span>
<span>B = arccot(x/10) </span>
<span>So, since θ = B-A </span>
<span>dθ/dt = dB/dt - dA/dt </span>
<span>= -3/(x^2+9) + 10/(x^2+100) </span>
<span>= 7(x^2-30)/((x^2+9)(x^2+100)) </span>
<span>so, at x=30 </span>
<span>dθ/dt = 203/30300</span>