Question 622300
The area of the right triangle is {{{A=(1/2) ab}}}
Where a and b are the legs of the right triangle
The shortest side {{{a=x-7y}}}  ft., the middle length side  {{{b=x + 6y}}}  ft.
Therefore the area is
{{{A=(1/2)(x-7y)(x+6y)}}}
Use FOIL method to open the brackets
{{{A=(1/2)(x^2+6xy-7xy-42y^2)=(1/2)(x^2-xy-42y^2)=(1/2)x^2-(1/2)xy-24y^2}}}{{{ft^2}}}