3x+y=1
x+1/3-y/5=2
y=1-3x
x-y/5=2-1/3
y=1-3x
(5x-y)/5=(6-1)/3
y=1-3x
(5x-(1-3x))/5=5/3
y=1-3x
(5x-1+3x)/5=5/3
y=1-3x
(8x-1)/5=5/3 |×15
y=1-3x
3×(8x-1)=5×5
y=1-3x
24x-3=25
y=1-3x
24x=28 | ÷24
y=1-3x
x=7/6
y=1-3×7/6
x=7/6
y=1-7/2
x=7/6
y=(2-7)/2
x=7/6
y=-5/2
x=7/6