If y=-8 when x=-3, find x when y=6.

Question

Please answer and show steps, this kind of math is called, direct and inverse variation. Thank you.

 

 

Variation is direct

Answer 1

Direct variation means y = k*x for some k

 

If y = -8 when x = -3 then 

 

-8 = k * (-3)  ==>  k = 8/3

 

So when y = 6 then 

 

6 = (8/3) * x  ==>  x = 18/8 = 9/4 

 

Answer 2

Both Edward and Barbara have approached this problem correctly. Edward's approach is for a pre-algebra/algebra level, whilst Barbara's is suitable for 4th-5th grade math problems teaching pattern recognition.

Answer 3

y = -8 when x = -3       y = 6     x = ?       y is 5 less than x       y = x - 5      6 = x - 5    Add 5 to both sides.

 

11 = x