① * ÷ ( 8 / 12 ) = 3 / 5
∴ * = ( 3 / 5 ) × ( 8 / 12 )
= 2 / 5
② ( 7* ) ÷ ( 1 / 3 ) = 3 / 5
∴ * = ( 3 / 5 ) × ( 1 / 3 ) × ( 1 / 7 )
= 1 / 35
③ ( 30 / 7 ) ÷ * = 18
∴ * = ( 30 / 7 ) ÷ 18
= ( 30 / 7 ) × ( 1 / 18 )
= 5 / 21
④ ( 2 / 3 )* = 8 / 9
∴ * = ( 8 / 9 ) × ( 3 / 2 )
= 4 / 3