There are a number of ways this can be done. One that is fairly simple is as follows.
Triangle ABC has base AC = 9 and height B to AC of 3 (found by counting squares). Thus its area is ∆ABC = (1/2)·9·3 = 13.5 square units.
Triangle ACF has base AC = 9 and height F to AC of 3, so will have the same area as triangle ABC, 13.5 square units.
Trapezoid CDEF has base CD of 6, base EF of 4 and height EF to CD of 6 (found by counting squares). Thus its area is CDEF = (1/2)(6 + 4)(6) = 30.
The total area of the entire figure is then
... ∆ABC + ∆ACF + CDEF = 13.5 + 13.5 + 30 = 57 square units.
