Question 1014865
Subtract 2 border widths from the side length
{{{ 7x - 2*12 = 7x - 24 }}} = width of court
not including border
Let {{{ A }}} = area of court not including border
{{{ A  = ( 7x - 24 )^2 }}}
{{{ A = 49x^2 -336x + 576 }}}