Question

If y=-4 when x=10, determine y when x=5

Answer 1

There's no way to answer that with the information given.

' Y ' might be -0.4x .  Then, when ' x ' is 5, ' y ' is  -2 .

OR,  ' y ' could be  x-14.  Then, when  ' x ' is  5, ' y ' is  -9 .
 
There's just not enough given information to know.