a charity group collected $6750 worth of donations on Saturday, Sunday and Monday. They collected $1251 less on Saturday than on Sunday. The amount collected on Sunday was 4 times the amount collected on Monday. What was the amount collected on Sunday?

Let's denote the amount collected on Saturday as $x, the amount collected on Sunday as $y, and the amount collected on Monday as $z.

According to the given information, we have the following equations:

1) The sum of the amounts collected on each day is $6750:
x + y + z = 6750

2) The amount collected on Saturday is $1251 less than the amount collected on Sunday:
x = y - 1251

3) The amount collected on Sunday is 4 times the amount collected on Monday:
y = 4z

To find the amount collected on Sunday, we need to solve this system of equations.

From equation 3), we can substitute y with 4z in equation 2):

x = 4z - 1251

Now, we can substitute x and y in equation 1) with their respective values:

(4z - 1251) + y + z = 6750

Combining like terms:

5z - 1251 + 4z = 6750

9z - 1251 = 6750

9z = 8001

Dividing both sides by 9:

z = 889

Substituting z back into equation 3), we can find y:

y = 4 * 889

y = 3556

Therefore, the amount collected on Sunday was $3556.

\textbf{Answer: The amount collected on Sunday was $3556.}