Question

dacax/y=2/5si3x+2y=640 aflati x si y

Answer 1

x/y=2/5
5x=2y
x=2y/5

3x+2y=640
3*2y/5+2y=640   umitor comun 5
6y +2y*5 = 640*5
6y+10y= 3200
16y=3200
y=200

x=2y/5
x=2*200/ 5
x=400/5
x=80

Answer 2

x/y=2/5 
3x+2y=640
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x=?  y=?
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x/y=2/5
x=5y/2
2x+2y=640
2*5y/2+2y=640
10y/2 +2y=640
5y+2y=640
8y=640
y=640/8
y=80

x=5y/2 => x=5*80/2 => x=400/2 => x=200