80% of 7.5 is 6.
so if he travelled 80% further, it would be 7.5+6 which is
13.5
X^4=256
x^4-256=0
(x^2)^2-(16)^2=0
(x^2+16)(x^2-16)=0
either x^2+16=0
it gives complex roots.
or x^2-16=0
or x^2-4^2=0
(x+4)(x-4)=0
either x+4=0,x=-4
or x-4=0
x=4
Drawing it out, as seen, using the Pythagorean theorem we get that w^2+l^2 (with w=width and l=length)=diagonal^2=24^2+l^2=40^2. Subtracting 24^2 from both sides, we get 40^2-24^2=l^2=1024. Square rooting both sides, we get l=32. Since the perimeter is 2w+2l, we get 32*2+24*2=64+48=112