The distributive property: a(b + c) = ab + ac
127 × 32 = 127 × (30 + 2) = 127 × 30 + 127 × 2 = (130 - 3) × 30 + (130 - 3) × 2
=(130)(30) - (3)(30) + (130)(2) - (3)(2) = 3900 - 90 + 260 - 6
= 3810 + 254 = 4064
127 × 32 = (130 - 3) × 32 = 130 × 32 - 3 × 32 = 130 × (30 + 2) - 96
= (130)(30) + (130)(2) - 96 = 3900 + 260 - (100 - 4) = 4160 - 100 + 4
= 4060 + 4 = 4064
Answer:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the hardness of a population, and for this case we know the distribution for X is given by:
Where
and 
We are interested on this probability

And the best way to solve this problem is using the normal standard distribution and the z score given by:

If we apply this formula to our probability we got this:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
After a little manipulation, the given diff'l equation will look like this:
e^y * dy = (2x + 1) * dx.
x^2
Integrating both sides, we get e^y = 2------- + x + c, or e^y = x^2 + x + c
2
Now let x=0 and y = 1, o find c:
e^1 = 0^2 + 0 + c. So, c = e, and the solution is e^y = x^2 + x + e.
Translate words into numbers.
13/(1 3/7)
First convert to improper fraction.
13/(10/7)
Then, note that division is the same as multiplying by the divisor's reciprocal.
13x7/10=9.1
answer: $9.10 per kilogram
7(x^2 +5x-7)
i think this is how it works