A reflection over the x-axis only change the signal of the coordinate y of the point. Hence, the coordinates of vertex B' are:

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Answer:
Step-by-step explanation:
Final step: Check your answer.
0.6x + 1.5 = 3.9
0.6x = 3.9 - 1.5
0.6x = 2.4
x = 2.4 ÷ 0.6
x = 4