Question

If y is proportional to x and y = -15 when x = -20, what is the value of x when y = 12?

Answer 1

Maybe i have that you wanted We can represent the situation like that: Y=-15 and x=-20 Then When y=12 x=? We make x(The unknown) *-15=12*(-20) We have an simple équation to solve Thus x=(12*(-20))/-15 X=16

Answer 2

X1= -20
x2= x2
y1= -15
y2= 12

x1  : x2 ::  y1 : y2
-20 : x   :: -15: 12

Means = x and -15
Extremes= -20 and 12

Product of mean = Product of extremes
       -15x = -20*12
            x = -240/-15
            x2 = 16