Answer :
The rule of the area of the rhombus using its 2 diagonals is
[tex]A=\frac{d1\times d2}{2}[/tex]Since the diagonals of the given rhombus are 20 mm and 7 mm
Then d1 = 20 and d2 = 7
Substitute them in the rule above
[tex]\begin{gathered} A=\frac{20\times7}{2} \\ A=\frac{140}{2} \\ A=70mm^2 \end{gathered}[/tex]The area of the rhombus is 70 square millimeters