The answer is the last one; to express very large or small numbers.
We use it so we can show big or very small numbers in an easier way.
The first reaction represented is a decomposition reaction due to the fact the bonded pair are being split apart.
The second equation is a single displacement because the B and C have switched places, which is the only change making it a single displacement. If there had been another bond and A had also moved, it would be double.
Answer: 15 grams
If he had 100 grams of candy bar, then 30% of that is 30 grams (since 30/100 = 30%). Cut this in half and we end up with 30/2 = 15.
Another way to find the answer is to multiply 50 and 0.30 which is the decimal form of 30%. So we have 50*0.30 = 15 which is the same answer.
2(x+2) > x+5
2x+4 > x+5
2x+4-x > x+5-x
x+4 > 5
x+4-4 > 5-4
x > 1