In the diagram below, $BE=EC=DF,$ and $\triangle ADF$ has the same area as $\triangle DEF.$ If rectangle $DXYF$ has area $42,$ what is the area of $\triangle ABC$?

Select the correct answer from each drop-down menu. a system of equations and its solution are given below. system a complete the sentences to explain what steps were followed to obtain the system of equations below. system b to get system b, the equation in system a was replaced by the sum of that equation and times the equation. the solution to system b the same as the solution to system a.]