To find the number in a square, we have to multiply two circles which are connected to it.So, to find a number in a circle, we have divide the number in the square by the number in the circle connected to it.Therefore, -6 Γ· -3 = 212 Γ· 2 = 66 Γ -3 = -18
Please find the attached photograph for their positions.
Hope you could get an idea from here
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