Answer:
a) (2+8)+9
b) (3+7)+5+4
c) (4+16)+2
d) (31+9)+4
Step-by-step explanation:
a) 2+9+8
2 and 8 add up to 10, so we regroup them in parentheses
(2+8)+9
b) 3 + 5 + 4 + 7
3 and 7 add up to 10, so we regroup them in parentheses
(3+7)+5+4
c) 4 + 2 + 16
4 and 16 add up to 20 which is a multiple of 10, so we regroup them in parentheses
(4+16)+2
d) 31 + 4 + 9
31 and 9 add up to 40 which is a multiple of 10, so we regroup them in parentheses
(31+9)+4
