s = side length of square
L = s-6 = width of rectangle (shorter side of rectangle)
W = s+1 = length of rectangle (longer side of rectangle)
multiply the length and width to get the area A
A = L*W
A = ( L ) * ( W )
A = (s-6)*(s+1) .............. substitution
A = s^2 + s - 6s - 6 ... use the FOIL rule
A = s^2 - 5s - 6 ......... combine like terms
Final Answer: s^2 - 5s - 6