6:
a: \(2.96\cdot\left(-5.25\right)\simeq3\cdot\left(-5\right)=-15\)
b: \(\left(-3.89\right)\left(-6.75\right)\simeq\left(-4\right)\cdot\left(-7\right)=28\)
c: \(\left(-6.31\right):5,92\simeq-6:6=-1\)
d: \(\dfrac{\left(-20.35\right)}{\left(-4.75\right)}\simeq\left(-20\right):\left(-5\right)=4\)