Assume that y varies directly with x, then solve.
if y=-6.6 when x=9.9, find y when x=6.6
y=?

y = - 4.4

Step-by-step explanation:

from the question

y = -6.6

x = 9.9

y∝ x

y = kx where k is introduced as a constant of proportionality

solve for k

y=-6.6 and x = 9.9

we have,

-6.6 = k × 9.9

-6.6 = 9.9k

divide both sides by 9.9

-6.6/ 9.9 = 9.9k/9.9

-0.667= k

therefore k = - 0.667

now, find y when x = 6.6

from the equation y = kx

y = -0.667 × 6.6

y = - 4.4

-4.4

Step-by-step explanation:

x : y

9.9 : -6.6

6.6 : y

9.9/-6.6 = 6.6/y

y = 6.6 × -6.6/9.9

y = -4.4