Verified answer

lg a + lg b = lg (ab)

lg a - lg b = lg (a/b)

㏒(3)x=3㏒(3)a-2㏒(3)b+㏒(3)(a+b)  

㏒(3)x=㏒(3)a³-㏒(3)b²+㏒(3)(a+b)

㏒(3)x=㏒(3) (a³*(a+b)/b²)

x = a³(a+b)/b²