Question 347266
3/7x+5/9y=27 multiply by 1/9
1/9x+2/7y=7 multiply by -3/7 & add.
1/9*3/7x+1/9*5/9y=1/9*27
3/63x+5/81y=3
-3/7*1/9x-3/7*2/7y=-3/7*7
-3/63x-6/49y=-3
3/63x+5/81y=3
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-6/81y+5/49y=0
y(-6/81+5/49)=0
y=0 ans
3/7x=27
3x/7=27 
3x=7*27
3x=189
x=189/3
x=63 ans.
Proof:
1/9*63+2/7*0=7
63/9=7
7=7