Answer:
The area of ΔDEF is 

Explanation:
we know that
If two triangles are similar, then the ratio of its corresponding sides is equal and this ratio is called the scale factor
and 
The ratio of its areas is equal to the scale factor squared
In this problem 
The corresponding sides of ΔABC and ΔDEF have equal lengths
therefore
the scale factor is equal to 

The triangles are congruent
therefore
ΔABC and ΔDEF has the same area