Question 106274
given:

Halley's Comet appears about every 75 years. 
One appearance was the year Mark Twain was born.  
Let this year be {{{x}}}

The next appearance was the year he died. 
Since Halley's Comet appears about every 75 years, means that Mark Twain lived 75 years too and died in year {{{y = x+75}}}

The sum of these two years is 3745. 

{{{x+(x+75) = 3745}}}

{{{2x + 75 = 3745}}}

{{{x = (3745- 75)/2}}}

{{{x = 1835}}}      the year Mark twain was born

{{{y = x+ 75}}}

{{{y = 1910}}}       In year {{{1910}}} Mark Twain died.