a) 3/2 - 1/2 : 3/4
= 3/2 - 1/2 * 4/3
= 3/2 - 2/3
= 9/6 - 4/6
= 5/6
b) 3/2 : { 2/9 * [ 5/2 - ( 1/5 + 1/2 ) * 5/2 ] - 1/7 }
= 3/2 : { 2/9 * [ 5/2 - ( 2/10 + 5/10 ) * 5/2 ] - 1/7 }
= 3/2 : [ 2/9 * ( 5/2 - 7/10 * 5/2 ) - 1/7 ]
= 3/2 : [ 2/9 * ( 5/2 - 7/4 ) - 1/7 ]
= 3/2 : [ 2/9 * ( 10/4 - 7/4 ) - 1/7 ]
= 3/2 : ( 2/9 * 3/4 - 1/7 )
= 3/2 : ( 1/6 - 1/7 )
= 3/2 : ( 7/42 - 6/42 )
= 3/2 : 1/42
= 3/2 * 42/1
= 63/1
= 63
