Question

elimination method
0.3x-0.2y=4
0.2x+0.5y= -21/23

Answer 1

Have a go at this yourself, I will start you off...
0.3x-0.2y=4 [1]
0.2x+0.5y= -21/23 [2]
Multiply [1] by 2 and [2] by 3
[1] becomes 0.6 -0.4y=8 call this [3]
[2] becomes 0.6 1.5y=-63/23 call this [4]

Now your part .....
Subtract line [4] from line [3]
to find that x disappears. You can then find y by division. Try it and let me know

Answer 2

Should read
[2] becomes 0.6 + 1.5y=-63/23 call this [4]

Answer 3

When you have found the value of y from this feed it into any of the two original equations to find x

Answer 4

I'm lost gianfranco

Answer 5

Where did youstart to get lost?

Answer 6

[1] becomes 0.6 -0.4y=8 call this [3]
[2] becomes 0.6 + 1.5y=-63/23 call this [4]
Subtract [4] from [3] gives ...
-1.9x = 8 + 63/23 = 170/23
-1.9x = 170/23
divide by -1.9 on both sides
x = 1167/347

Answer 7

Let us try something else
0.3x-0.2y=4
0.2x+0.5y= -21/23
Multiply everything by 10
3x -2y = 40 [1]
2x + 5y =-210/23 [2]
Multiply [1] by 2 and [2] by 3
6x -4y = 80 [1]
6x + 15y =-630/23 [2]
Now subtract [2] from [1]
-19y = 728/23
divide by -19
= 728/23
now y= 728/23
feed this into any of your equations as the value of y and you will calculate x