DF = 3
Explanation:
If ABC is equivalent to EDF, then DF is equivalent to BC, which form the following ordered pairs:
D = (0,2)
F = (3,2)
It can be seen that both pairs have the same value of "y" or second value, that is 2.
As a rule, when the points are located on the y-axis (of the ordinates) or on a line parallel to this axis, the distance between the points corresponds to the absolute value of the difference of their ordinates.
So,
DF = D(x) + F(x) = 0 + 3 = 3