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$${\mathtt{1\,400}}{\mathtt{\,\times\,}}{\mathtt{16}} = {\mathtt{22\,400}}$$    This is the number of watt-hours (Wh ) in a month

this is equal to 22,400 kWh.

9(cent/kWh)*22,4kWh=...cent

It's a function that describes a line. 

the value is 7 times the value of x. And add 9 to that value

the line intersect with the vertical axis in a coordinate system when y=9.

the number in front of x decides the slope

Just divide 17000 with 120000 and multiply the answer with hundred to get the answer in percent.

$${\mathtt{100}}{\mathtt{\,\times\,}}\left({\frac{{\mathtt{17\,000}}}{{\mathtt{120\,000}}}}\right) = {\frac{{\mathtt{85}}}{{\mathtt{6}}}} = {\mathtt{14.166\: \!666\: \!666\: \!666\: \!666\: \!7}}$$

the answer is 14,17%

...and what´sthe question?

$${\mathtt{7}}{\mathtt{\,\times\,}}{\mathtt{4\,562\,189\,555\,554}} = {\mathtt{31\,935\,326\,888\,878}}$$

That was nice!!

8 batteries costs 5.99

1 battery should cost 1/8 of the price of 8 batteries.

therefore 1 battery cost     $$5,99/8=$$

the median is the value in the middle.

if you got 1,3,4,4,5,6,7,8,9 then 5 is your median because it is in the middle.

What if you got 5,9,3,11,2,8,4,6?

then you sort the values from smallest to largest: 2,3,4,5,6,8,9,11. the value in the middle is the median.

in this scenario we got two numbers in the middle so in this case the median is the average of the two values in the middle (5+6)/2 =13/2=6,5

:)

for example x=4

and y=0,05

to solve this you need one more equation otherwise it´s not possible to solve it.