Answer:
12,000
Step-by-step explanation:
Let "a" represent the number of panels produced by Plant A. Then the number produced by Plant B is (a+7000). The total number of defectives is ...
... 0.04a + 0.02(a+7000) = 860
... 0.06a + 140 = 860 . . . . . . . . . . . . . simplify
... a = (860 -140)/0.06 = 12,000 . . . . solve for a
Plant A produced 12,000 panels yesterday.
