The variation given in the first question is not a direct variation and there is no constant of variation.
Direct variation
y = k × x
when
y = -40 and x = -0.5
y = k × x
-40 = k × -0.5
-40 = -0.5k
k = -40/-0.5
k = 80
When y = 8 and x = 2.5
y = k × x
8 = k × 2.5
8 = 2.5k
k = 8 / 2.5
k = 3.2
When y = 4 and x = -3
y = k × x
4 = k × -3
4 = -3k
k = -4/3
when y = 8 and x = -6
y = k × x
8 = k × -6
8 = -6k
k = 8/-6
k = -4/3
This is a direct variation and the constant of proportionality is -4/3
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