Yvaries directly affects if y equals negative five when x equals 15 find x when y equals three

Well,

We are given a direct proportion problem.

x varies directly as y.



When y = -5, x = 15.


Now, we are told to find x when y = 3.



We just have to recognize that the complete case is equal to the incomplete case.  In other words, we set the -3 equal to the x/3.



Multiply both sides by the LCM.
LCM of -1 and 3 = 3

-9 = x

When y = 3, x = -9.

The equation is y=17(7)+600 and it equals 717