I think D is the correct answer.
Combine like terms
9r+r=10r^2
7b+b=8b^2
10+10r^2+8b^2+4n
You would just subtract/add like you normally would from left to right because its a subtract and add operation.
Hope that helps :)
The probability is low.
20% of 9 is 2. Therefore, the probability is low that 5 out of the 9 students drive cars.
