我不会这一题，请大家说说应该怎样做，题目如下：?

2.
Join AC.

AC = AC (common)
AE = AF (given)
∠AEC = ∠AFC = 90° (given)
Hence, ΔAEC ≅ ΔAFC (RHS)
Area of ΔAEC = Area of ΔAFC

Area of quad. AECF = 32 cm²
(Area of ΔAEC) + (Area of ΔAFC) = 32 cm²
Area of ΔAFC = 16 cm²

Area of rhombus ABCD = 80 cm²
Area of ΔADC = 40 cm² (diagonal equally bisects the rhombus)

ΔAFC and ΔADC have the same altitude CF.
(Area of ΔAFC) : (Area of ΔADC) = AF : (AF + DF)
16 : 40 = AF : (AF + DF)
40AF = 16AF + 16DF
24AF = 16DF
AF = (2/3)DF
AF = (2/3) × 6 cm
AF = 4 cm