a) ( 5/6 + 1 5/8 ) : (1/2)^2 - 9 1/3 =
= ( 5/6 + 13/8 ) : 1/4 - 28/3 =
= 59/24 × 4 - 28/3 =
= 59/6 - 28/3 = 1/2
b) [( 3 - 2 3/7 )× 3 1/2- 3/21 -15/35 ] × 11/5 =
= (( 3 - 17/3 ) × 7/2 - 3/21 - 15/35 ) × 11/5 =
= ( 2 - 3/21 - 15/35 )× 11/5 =
= 10/7 × 11/5 =
= 2/7 × 11 = 22/7