Let's say I have 4 values A, B, C and D. Let's say they each contribute 30%, 30%, 20% and 20% towards some final value X.

So my weighted average formula is:

X = [0.3(A) + 0.3(B) + 0.2(C) + 0.2(D)] / [0.3+0.3+0.2+0.2]

But what if the situation is such that values C and D contribute negatively to the over all value X?

As a sports analogy using a hypothetical situation, let's say I am calculating a Football Quarterback's rating using my own method as follows:

A = Yards per Attempt (I want this to be high, so this is a positive value) - 30% weight
B = Number of Touchdowns (I want this to be high, so this is a positive value) - 30% weight
C = Number of Incomplete passes (I want this number to be low/miniumum and it contributes negatively to the overall rating) - 20% weight
D = Number of Interceptions (Needs to be minimized and contributes negatively to the overall rating) - 20% weight

So for my overall weighted average QB rating can I use this formula?

X = [0.3(A) + 0.3(B) - 0.2(C) - 0.2(D)] / [0.3+0.3+0.2+0.2]

If this is wrong, how to I account of positive and negative numbers in the same weighted average formula? Do the positives and negatives have to add up to 100% individually? But what if they contribute different amounts to the end result?