78 gallons is the same as 312 quarts
Let's say Jackson's age now is x.
In 20 years, (so 20+x), Jackson seven years ago will be 2/5ths of that age.
So 2/5(20+x)=x-7
Then you solve the equation
8+2/5x=x-7
15=3/5x
x=25
Jackson is 25 years old.
Let's check our answer! In 20 years, Jackson will be 45. 7 years ago, he was 18. 2/5 of 45 is 18. Our answer is correct!
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Answer:
C. {x² + 4, x < 2
{-x + 4 x ≥ 2
Step-by-step explanation:
This is a piecewise function, where the two equations are different. They are:
y = x²+ 4
y = -x + 4
The function x² + 4 is graphed where x < 2. (< is used because the circle is open)
The function -x + 4 is graphed where x ≥ 2. (≥ is used since the endpoint is closed)
Therefore, the correct answer is:
C. x² + 4, x < 2
-x + 4 x ≥ 2
There's some unknown (but derivable) system of equations being modeled by the two lines in the given graph. (But we don't care what equations make up these lines.)
There's no solution to this particular system because the two lines are parallel.
How do we know they're parallel? Parallel lines have the same slope, and we can easily calculate the slope of these lines.
The line on the left passes through the points (-1, 0) and (0, -2), so it has slope
(-2 - 0)/(0 - (-1)) = -2/1 = -2
The line on the right passes through (0, 2) and (1, 0), so its slope is
(0 - 2)/(1 - 0) = -2/1 = -2
The slopes are equal, so the lines are parallel.
Why does this mean there is no solution? Graphically, a solution to the system is represented by an intersection of the lines. Parallel lines never intersect, so there is no solution.
