The common denominators would be 2,8,6,1
A - a removes both a’s from equation, then you’re left with b + bsquared, since they are unknown values you cannot combine them, even if it is the same letter, you can only add and subtract unknown values with their same letters together.
Mean is a form of average, and in order to find this we add up all the numbers then divide by the amount of numbers we have.
So, we have 5 numbers here. (8, 17, 9, 3, and 13)
8 + 17 + 9 + 3 + 13 = 50
50/5 = 10
The mean of those five numbers is 10.
Please note that you have to use the reason vert. opp. angles to find x, hope it helps:)
