the complete question in the attached figure
we know that
(see the attached figure n 2 to understand the problem)
[the surface area of one prism]=2*[x*x]+2*[x*y]+2*[x*y]----> 2x²+4xy
[the surface area of the sculpture]=2*[5*x*y]+2*[3*x*x]+2*[3*x*y]--> 6x²+16xy
now
JD says the surface area of the sculpture is 4 times the surface area of one prism
[the surface area of the sculpture]=4*(2x²+4xy)---> 8x²+16xy
we compare the value that JD says with the real value
(8x²+16xy) > (6x²+16xy)
the value that JD says is greater in comparison with the real value
This is because JD should also subtract the areas of eight hidden surfaces.
the answer is
JD should also subtract the areas of eight hidden surfaces