57 mm²
1) Since we have a polygon made of two figures we can calculate it this way:
2) Since for the vertical rectangle
S= wl Rectangle's area
S= 3 x 9 = 27 mm²
and for the "horizontal one"
S= 6 x 5
S = 30 mm²
3) Adding it all up, we have
S =30 +27 = 57 mm², and that is the answer.
