Check the picture below.
now, since we know what "f" is, let us use the CNT triangle with the small COR one.

The mean = 2,000
s = Sigma ( standard deviation ) = 300
M - 2 s = 2,000- 2 * 300 = 2,000 - 600 = 1,400
M + 2 s = 2,000 + 2 * 300 = 2,000 + 600 = 2,600
Answer.
Useful life of light bulbs within 2 standard deviations of the mean is:
A ) Between 1,400 and 2,600 hours
Answer:
x=4.25
Step-by-step explanation:
4x=17
4x/4=17/4
x=17/4
or
x=4.25
Hope this helps .-.
4 thousands = 4,000
21 tens = 21*10 = 210
210 + 4,000 = 4,210
Answer: 4,210