Complete the equation of variation where y varies inversely as x and y = 8 when x = 10.

Inverse variation is of the form y=k/x, or if you prefer yx=k.  "Inverse" variation because as x increases, y decreases...Anyway the equation can be expressed as:

y=k/x, we are given one point (10,8) so we can find the value of k, the constant of variation using those coordinates...

8=k/10  multiply both sides by 10

80=k so the equation is:

y=80/x

The correct answer is c.