d=-5.5 should be the answer

she should have invested P, in order to get I = 6500
but she instead invested 17,801, how much more did she need? well, P - 17801
solve for P
In order to solve this we need to make on part of both statements equal.
Since 12 is divisible by 6 lets do that.
Multiply everything in the second package by 2.
It then becomes 6 pairs for $12.
So now have have 6 or 8 pairs for $12.
You are getting a different amount for the same price therefore they are not proportional.
Let the numbers be x and y.
x*y=HCF*LCM=6*60=360
thus
y=360/x
next we find the list of combinations of x and y and test if they satisfy the conditions above:
(6,60),(12,30),(18,20),(24,15)
out of the above, only (6,60) and (12,30) satisfy both conditions. Thus our answer is:
(6,60) or (12,30)