2lg(5/3)-lg(7/4)+2lg3+1/2lg49
=lg(5/3)^2-lg(7/4)+lg3^2+lg49^(1/2)
=lg(25/9)-lg(7/4)+lg9+lg7
=lg[(25/9)*9*7÷(7/4)]
=lg(25*7*4÷7)
=lg100
=lg10^2
=2