Find the area of △DEF with vertices D(−4, −2), E(−1, −8), and F(−7, −8). The AREA of △DEF is square units. *

If you plot these points you will see that the base is 6 (distance from E to F, count the squares).

The height will be 6 ( distance from line EF to D, again count the squares).

Using the Area formula you get A = 1/2 (6) (6) = 18

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.