$\text{a)}-32:\left(16:8\right)=-632:2=-16$  

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$\text{b)}\left(-7+9\right)\cdot \left(3-5\right)=2\cdot \left(-2\right)=-4$  

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$\text{c)}4-4\cdot 7+5-5\cdot 2+3-3\cdot 4=4-28+5-10+3-12=12-50=-38$