Question 64191
LARGE = 3.00
small = 2.00
657 boxes on day
1612 total on day
Let L be the number of boxes of LARGE
Let s be the number of boxes of small
L + s = 657
L * 3.00 + s * 2.00 = 1612.00
two equations and two unknowns

Let's subsitute for L using s, from the L + s = 657 equation.
L + s = 657
    L = 657 - s

and plugin to the second equation, gives

( 657 - s ) * 3.00 + s * 2.00 = 1612.00

1971 - s * 3.00 + s * 2.00 = 1612.00

subtract 1971 from both sides

-s * 3.00 + s * 2.00 = 1612 - 1971
-3 s + 2 s = 1612 - 1971
-1 s = 1612 - 1971
-s = -359
or s = 359.

Plug this new found value for s back into the original equation, 
and get L

L + s = 657
L + 359 = 657
L = 657 - 359
L = 298


So, in answer to how many of each boxes were sold on that day,
298 Large and 359 small boxes were sold.