X= (k+c):(m- ny/b)=(k+c): (mb-ny)/b= (k+c)*b/(mb-ny)
x= (bc+bk)/bm-ny
D is correct
The estimate is low because both factors are rounded up.
True, without representation the colonies abilities to dispute in subjects such as taxes were hindered, causing their unhappiness.

the answer to the question
it's really just your own opinion of which is difficult or easier but in my opinion Substitution is more difficult because you have to substitute in the different equations, and it can take more time. I personally like Elimination best because it cancels out variables and can be quicker to use. hope this helps:)