Ineed the answer i have isn't working

difference = 3 ft²

Surface area of box J

= 2( 4.5 × 3 ) + 2( 2 × 3 ) + 2( 4.5  × 2 ) = 27 + 12 + 18 = 57 ft²

Surface area of box F

note that F is a cube with 6 square faces = 6( 3 × 3 ) = 54 ft²

difference = 57 - 54 = 3 ft²

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.