3*3^[3(n+1)]*3^[4(n-1)]=3^49
3^[1+3(n+1)+4(n-1)]=3^49
1+3(n+1)+4(n-1)=49
7n=49
n=7
x+y=2 (1)
3x+7y=10 (2)
(1)×7-(2)
7x-3x=14-10
x=1
y=2-x=1