Let the shorter piece be called "x"
The longer piece is "3" less than TWICE shorter, so we can write the equation:
Longer is:
Since the board is 12 feet, we can say:
Longer + Shorter = 12
we know longer = 2x - 3 and shorter is x, so we can write:
(2x - 3) + (x) = 12
We simply solve this equation for "x":
So, shorter piece (x) is 5 feet
Longer piece, thus, is 12 - 5 = 7 feet