Her is what I understand as your table top.
I let the long side length by s inches and each of the six short side lengths be x inches.
Here is a closer look at one of the ends.
The triangle shown is a right triangle and hence, by Pythagoras Theorem,
y2 + y2 = x2 or 2 y2 = x2 and hence y = x/√2
Thus the width of the table, 48 inches, can be written
48 = y + x + y = x/√2 + x + x/√2 = (1 + 2/√2 ) x = (1 + √2) x
x = 48/(1 + √2) = 19.88" or 19 7/8 inches
Thus the length of the long side is
s = 72 - 2 (19 7/8 ) = 32 1/4 inches.