-7x + 8y = 19 5x + y = 20

1 answer:

8 0

X = 3
y = 5
(3,5)
I used substitution because It seemed the easiest.
From the second equation I isolated it for Y to get y=20-5x

I plugged this in to the other equation for the Y value to perform substitution.

-7x + 8 (20-5x) = 19
then it's simple algebra

-7× + 160 - 40x = 19
-47x + 160 = 19

subtract 160 from both side and divide both side by -47 to isolate x.

-47x = -141
x=3

then to find Y, simple plug this into one of the equation above. or simply use this one that we already isolated for Y:
y=20-5x
y=20-5 (3)
y=5

hope that helps

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Laboratory tests show that the lives of

SIZIF [17.4K]

<h3>Answer: 34%</h3>

This result is approximate.

=========================================================

Explanation:

mu = 750 = mean

sigma = 75 = standard deviation

The raw scores or x values are x = 750 and x = 825

Let's compute the z score for each x value

z = (x - mu)/sigma

z = (750 - 750)/75

z = 0

and

z = (x - mu)/sigma

z = (825 - 750)/75

z = 1

Therefore P(750 ≤ x ≤ 825) is equivalent to P(0 ≤ z ≤ 1) in this context.

Use a z score table to determine that

P(z ≤ 0) = 0.5

P(z ≤ 1) = 0.84314 approximately

So,

P(a ≤ z ≤ b) = P(z ≤ b) - P(z ≤ a)

P(0 ≤ z ≤ 1) = P(z ≤ 1) - P(z ≤ 0)

P(0 ≤ z ≤ 1) = 0.84314 - 0.5

P(0 ≤ z ≤ 1) = 0.34314 approximately

The value 0.34314 then converts to 34.314% which rounds to 34%

Or you could use the empirical rule as shown below. The pink section on the right is marked 34% which is approximate. This pink section is between z = 0 and z = 1.