Answer:
The dimensions of the tabletop: Length= 67.976... inches and Width= 33.988... inches and the perimeter will be 203.929... inches.
Explanation:
Suppose, the width of the rectangular tabletop is
inch.
As the tabletop has a length that is twice it’s width, so the length will be:
inch.
The tabletop measures 76 inches on its diagonal.
Formula for length of diagonal of rectangle:

So, the equation will be..........

Thus, the width of the tabletop is 33.988... inches and the length will be: (2×33.988...) = 67.976... inches.
The perimeter will be: 2(33.988...+ 67.976...) inches = 203.929... inches.