Suppose the order quantity of blue socks is x pairs.
( 1 + 30%)? [4? 1 + (2/3)? x]= 1？ x + 4？ (2/3)
1.3(4 + 2x/3)=x + 8/3
5.2+2.6 times /3-x=8/3
-0.4x/3=8/3 - 15.6/3
-0.4x/3=-7.6/3
x= 19
Answer: The order number of blue socks is 19 pairs.