So you have the ratio of 9:2. 
The video has 18 thumbs up votes with the ratio being thumbs up to thumbs down. 
9 in relation to 18 is times 2 so it makes since to times 2 by 2. 
Therefore the ratio would be 18:4 which means there would be 4 thumbs down. 
 
        
             
        
        
        
Id say the first one because the points just touch down
        
             
        
        
        
Combining the operations
The allowed operations are:
Add the same amount to both sides (either x's or ones)
Subtract the same amount from both sides (either x's or ones)
Multiply both sides by the same number (but not by zero)
Divide both sides by the same number (but not by zero)
(There are others, too, but they are not needed in simple equations.)
The goal is to FIRST add and subtract until we have ONLY x's (blocks) on one side and ONLY ones (circles) on the other. Then, if you have more than one block, you need to divide so as to arrive to the situation with only one block on the one side, which is the solved equation!
        
                    
             
        
        
        
So I'm assuming that you're taking Calculus.
The first thing you want to do is take the integral of f(x)...
Use the power rule to get:
4X^2-13X+3.
Now solve for X when f(x)=0. This is because when the slope is 0, it is either a minimum or a maximum(I'm assuming you know this)
Now you get X=0.25 and X=3. Since we are working in the interval of (1,4), we can ignore 0.25
Thus our potential X values for max and min are X=1,X=4,X=3(You don't want to forget the ends of the bounds!)
Plugging these value in for f(x), we get
f(1)=2.833
f(3)=-8.5
f(4)=1.667
Thus X=1 is the max and X=3 is the min.
So max:(1,2.833)
min:(3,-8.5)
Hope this helps!