Which ordered pair is the solution to the system of equations?

2x+y=-8
x−y=−4

1. (1, 5)

2. (−1, 3)

3. (−4, 0)

4. (−3, −2)

#3. (-4,0)

Step-by-step explanation:

Add the two equations

2x + y = -8

x - y = -4. The y's cancel

3x +0 = -12. Divide both sides by 3

x = -4 Substitute for x in the first equation and solve for y.

2(-4) + y = -8

-8 + y = -8

y = 0

Solution: (-4,0)

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

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