For this case we have the following data:


So that the figure can be a rectangle, its diagonals must be equal, that is, 
In this way we have:

Clearing x we have:


Thus, x must be equal to 10 so that the figure is a rectangle.
Answer:

Option A
A = 3.5
b = 3.5
c = 2.5
d = 2.85
e = 2.6
The two unit rates that are equal are a and b
28 per 8 salads and 42 per 12 steaks have equal unit rates.
The numbers would be 22 and 4