Question

Solve by substitution
5x-21=-y
2x-y=0

Answer 1

y=2x

Answer 2

what does -y equal?

Answer 3

than
5x+2x=21
7x=21
x=21/7
x=3

Answer 4

Thats the problem you are suppose to solve by substitution

Answer 5

do they tell you what -y equals or do you just have to guess at it?

Answer 6

so than y= 2*3 =6

y=6

Answer 7

it doesnt say

Answer 8

perhaps your not understanding the question im asking :)

it isnt about what solid value you can attribute to -y like saying -y=28 or some such; but its a related value

Answer 9

does it give you some sort of indication as to what -y COULD be?

Answer 10

thats the exact from my paper what i type

Answer 11

im sure it is ...

Answer 12

5x-21= -y

would you agree from this here that -y equals some relation to 5x-21 ?

Answer 13

x = 21/5, y = 0

Answer 14

this is key to understanding how substitution works to solve these

Answer 15

it tells you in the problem that "-y" is equal to some relation such that "-y" equals "5x-21".

Answer 16

and since -y = 5x-21; wherever we see a "-y" we can replace it by "5x-21"

the second equation gives us this situation:

2x -y = 0 ; we can substitute in the "value" of -y in here since it is equal to it to begin with

2x + (5x-21) = 0

Answer 17

ok heres another problem solve by substitution
15x-20y=-1
5y=-1+10x

Answer 18

how are we to solve it?

Answer 19

by substitution

Answer 20

by substitution doesnt mean that you get someone else to solve it for you :)

Answer 21

what value can we relate to x or y ?

Answer 22

duh im here for help not sarcasm

Answer 23

then take the help ....

Answer 24

i dont need yours goodbye

Answer 25

oh but you do, you do ...

by this type of problem, we should e familiar with how to manipulate and equation to solve it for a particular part thru algebraic means

Answer 26

if we cant yet solve for either an x or a y in terms of the information given; then there is no real hope of getting to a solution

Answer 27

toodles someone will have a better attitude then yours

Answer 28

by chance they might; or they might be satisfied with simply touting off an answer and leaving you in your ignorance.

Answer 29

i would rather attempt to teach you how to get a solution for yourself and empower you for the future

Answer 30

i am going to report you thanks for the comments.

Answer 31

and your report will be sent to me in an email and I will read it and make a choice on what action I should take as a result ... that is what a moderator does

Answer 32

in the mean time, you will continue to sidestep the real issue here and take offense to someone actually taking the time to try to enlighten you

Answer 33

We'll see about that

Answer 34

Now given your equations:

15x-20y=-1
5y=-1+10x

do you recall any means whereby we can single out an x or a y that we can use to substitute into the other with?

Answer 35

given that i dont have the time needed to sit here and try to help you; i have to run to class for a few hours. Maybe someone will come along and give you the guidance you are seeking.

Good luck with it :)