Answer:
d = 8 mm
Explanation:
You want the length of the other diagonal of a rhombus when one of them has length 35 mm and the area of the rhombus is 140 mm².
Area
The area of a rhombus is half the product of the lengths of the diagonals:
A = 1/2(d1)(d2)
140 mm² = 1/2(35 mm)(d)
(280 mm²)/(35 mm) = d = 8 mm
The length of the missing diagonal is 8 mm.