#### Answer

$\color{blue}{B \cap A = \left\{4, 8\right\}}$

#### Work Step by Step

Given:
$A=\left\{1, 3, 4, 5, 7, 8\right\}$
$B=\left\{2, 4, 6, 8\right\}$
RECALL:
$B \cap A$, the intersection of sets B and A, is the set the contains the elements that are common to sets A and B.
Notice that the elements common to A and B are: 4 and 8
Thus,
$\color{blue}{B \cap A = \left\{4, 8\right\}}$