In plain and short, we simply divide 5 by (1+2+3) and then distribute the pieces likewise

add the ratios up, and you'll get 5.
6+x is an example of an expression. if it was a variable it would be 6x.
Answer:
Remember rise over run for the slope.
the slope is always the number on the left side (x) and the y intercept is the number in the right (y)
(x,y).
It would be b. the first ratio is
1kL
----
1000
so you would match up the kL and not know how many regular liters there are.
8kL
-----
x