3^(3x+1)*5^(2x+1)=15^3*15^(2x+1)
3^(3x+1)=15^3*15^(2x+1)/5^(2x+1)
3^(3x+1)=15^3*3^(2x+1)
3^(3x+1)/3^(2x+1)=15^3
3^x=15^3
x=log3(15^3)
即x=3log3(15)