a. 25 × 4 - 189 : 9 =
= 100 - 21 =
= 79
b. ( 16 + 3 × 9 + 37 ) : 10 =
= ( 16 + 27 + 37 ) : 10 =
= ( 43 + 37 ) : 10 =
= 80 : 10 =
= 8
c. 91 - [ 88 + ( 50 - 72 : 9 ) : 6 ] : 5 =
= 91 - [ 88 + ( 50 - 8) : 6 ] : 5 =
= 91 - ( 88 + 42 : 6 ) : 5 =
= 91 - ( 88 + 7 ) : 5 =
= 91 - 95 : 5 =
= 91 - 19 =
= 72.
