Answer:
2.5, - 1200
Explanation:
(a)
Substitute the given values into the expression
= = = = = 2.5
(b)
2a × b × 5c
= 10abc
= 10 × - 5 × - 6 × - 4
= - 50 × 24
= - 1200
a)2.5 b)-1200
a)2(-5)/4=-10/-4=5/2=2.5
b)2(-5)×(-6)×5(-4)=-10×-6×-20=-1200
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= 
= 
= 
= 
= 2.5