Answer:C
Step-by-step explanation: You want to add up all the marbles, and then take the red marbles and divide by all the marbles 7/20
Answer:
0.45 m, 0.63 m, 0.72 m
Step-by-step explanation:
Let the three parts of the line be 5x, 7x and 8x
Therefore,
5x + 7x + 8x = 1.8
20x = 1.8
x = 1.8/20
x = 0.09
5x = 5*0.09 = 0.45 m
7x = 7*0.09 = 0.63 m
8x = 8*0.09 = 0.72 m
Start by writing the system down, I will use
to represent 

Substitute the fact that
into the first equation to get,

Simplify into a quadratic form (
),

Now you can use Vieta's rule which states that any quadratic equation can be written in the following form,

which then must factor into

And the solutions will be
.
Clearly for small coefficients like ours
, this is very easy to figure out. To get 5 and 6 we simply say that
.
This fits the definition as
and
.
So as mentioned, solutions will equal to
but these are just x-values in the solution pairs of a form
.
To get y-values we must substitute 3 for x in the original equation and then also 2 for x in the original equation. Luckily we already know that substituting either of the two numbers yields a zero.
So the solution pairs are
and
.
Hope this helps :)