Let me list the options, without any real knowledge of the actual penalties:
1 - Red declines the illegal forward pass penalty. White gets the ball at the 31.
- If White also declines the roughing penalty, the ball stays there - at the 31
- It White accepts the penalty, tack on 15 - White ball at the 16
2 - White declines the penalty on red
- If Red accepts the ifp penalty, it is White ball on the 50, loss of down - they are punting
- If Red declines the penalty on white, again, it is 1st and 10 at the 31
3 - Neither team declines the penalty - both are marched off
- 5 yards and loss of down, move the ball back to the 50
- 15 yards and automatic first down, move the ball up to the 35
so the four options are
* White ball at the 16 (requires Red to decline penalty)
* White ball at the 50 and punting (requires White to decline penalty)
* White ball at the 31 (both teams decline penalties)
* White ball at the 35 (both teams accept penalties)
Since being the only team to decline a penalty hurts your outcome, both would be inclined to accept the penalties.
What did I mess up?