Without a calculator, find gcd(20!+95, 19!+5). I think it is $5$ because the gcf of just $20!$ and $19!$ is $19!$, and with the addition it cancels the other factors.

$\gcd(20! + 95, 19! + 5)=$
$\gcd((20! +95)-20(19! + 5), 19! + 5)=$
$\gcd(95 - 100, 19!+5)=$
$\gcd(5, 19! + 5) = $
$5\gcd(1, \frac {19!}5 + 1)=$
$5*1 =5$
