Answer
There were 14,000 fans on Sunday's game while there were 42,000 fans on Saturday's game.
Work Step by Step
Let $x = $ attendance on Sunday's game
$3x + x = 56,000$
$4x = 56,000$
$x = \frac{56,000}{4}$
$x = 14,000$ fans
Let $y =$ attendance on Saturday's game
$y = 3x$
$y = 3(14,000)$
$y = 42,000$ fans