X could be any positive number (a fraction, 1, or greater than1)
If x is 1, both columns will be equal, otherwise they are not ...and so the answer is D.

If BC were a diameter then the marked angle would be 90.
Since we are told that it is not a diameter, the measure of the angle could be less or more depending on where we draw the chord.

1cm² is the equivalent of 100mm²
So the right side is much less since it is only 10mm²

Be careful when the figure is not to scale. Redraw exaggerating the shape. (For example, you could put A and E in line). You will then find that although they look equal here, BC and CA are not necessarily equal. (But they could be sometimes.) Hence this is a D answer.

If you are not confident of fractions, convert to decimals.
So 7/8 = 0.875, 5/6 = 0.8333and 6/7 = 0.857 (approx)
Now we can see that 6/7 does lie between the given fractions, but x could be bigger or smaller and still lie between 0.875 and 0.8333

A fifteen percent discount means that you get the item at 85 percent of its original price.
85 percent of t is the equivalent of 0.85t

This is a quadratic equation. Factorize into (x - 5)(x - 7) = 0
So x must be either 5 or 7. Both answers are less than 12.

Frame the information into a mathematical statement. Twice the number of students in class B = 2x.
The number in class A is 10 less, i.e. 2x - 10. So both are equivalent.

Try a couple of even numbers for n. Take 10 for example. The remainder on the left will be 1, and on the right, 0. But taking 12, will give remainder 0 on the left, and 2 on the right. These two situations are sufficient to determine the answer must be D.

The number 1 raised to any power is always 1. So 2⁸ is obviously much larger.