Start with

Add 2x to both sides:

Subtract 21 from both sides:

Divide both sides by 5. Since it is positive, we don't have to change the inequality sign:

So, the answer is 
Answer:
zero(0)
Step-by-step explanation:
The additive identity of a set of number is a number such that the its sum with any of the numbers in the set would give a result that is equal to the number in that set.
In other words, say for example the set of numbers is rational, the additive identity of rational numbers is 0. This is because, given any rational number say <em>x</em>, adding zero to the number <em>x</em> gives the same number <em>x. </em>i.e
x + 0 = x
If x is say 2, then we have;
2 + 0 = 2
Since adding zero to rational numbers gives has no effect on the numbers, then zero (0) is the additive identity of rational numbers.
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"Better to have loved a short man than never to have loved a tall".
Answer:
C
Step-by-step explanation:
Parabola with a vertex at (1, 3) opening downward.