Răspuns :
12/25=x/15...=>12/25-x/15=0
12*3-(x*5) 36-5x
-------------- = ----------
75 75
36-5x
-------- =0
75
36-5x
------- * 75=0*75
75
-5x+36=0....=> -5x=-36....=>5x=36
36
x= --- =7,200
5
----------------------------------------------------------------------------------------
28/x=21/7.....=>28/x-(21/7)=0
28
--- -3=0
x
3 3*x
3=--- = ------
1 x
28-(3*x) 28-3x
----------- = --------
x x
28-3x 28-3x
------- =0 => ----------- *x =0*x
x x
28-3x=0
-3x+28=0
-3x=-28
3x=28
x=28/3=9,333
-------------------------------------------------------
x/125=12/25
x/125-(12/25)=0
x/25-12/25=0
x-(12*5) x-60
------------ = --------------
125 125
x-60
------ =0
125
x-60
------ *125=0*125
125
x-60=0
x=60
12*3-(x*5) 36-5x
-------------- = ----------
75 75
36-5x
-------- =0
75
36-5x
------- * 75=0*75
75
-5x+36=0....=> -5x=-36....=>5x=36
36
x= --- =7,200
5
----------------------------------------------------------------------------------------
28/x=21/7.....=>28/x-(21/7)=0
28
--- -3=0
x
3 3*x
3=--- = ------
1 x
28-(3*x) 28-3x
----------- = --------
x x
28-3x 28-3x
------- =0 => ----------- *x =0*x
x x
28-3x=0
-3x+28=0
-3x=-28
3x=28
x=28/3=9,333
-------------------------------------------------------
x/125=12/25
x/125-(12/25)=0
x/25-12/25=0
x-(12*5) x-60
------------ = --------------
125 125
x-60
------ =0
125
x-60
------ *125=0*125
125
x-60=0
x=60