Question

For each function, y varies directly with x. Find each constant variation. Then find the value of y when x= -0.3.

1. y=2 when x= -1/2

2. y= 2/3 when x= 0.2

3. y=7 when x= 2

4. y=4 when x= -3

Answer 1

You meant "find the constant of proportionality"

Given y=2 when x= -1/2, and looking for a formula such as y = k*x, 
substitute the given value (2) for y and the given value (-1/2) for x:

2 = k * (-1/2).  Solve this for k.      Then write out the general formula y = k * x, and let x= -0.3.