Question

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

Answer 1

y= k·x
if y= -15 and x= -20
⇒ -15 = k·(-20)
⇒ k = -15/-20 
⇒ k = 3/4

What is the value of x when y=12 ?

x= ?
k= 3/4
y = 12

y = kx
⇒ x = y/k
⇒ x = 12/(3/4)
⇒ x = 12· (4/3)
⇒ x = 16