Answer:
10. 39
12. $21.49
14. 9.89
Explanation:
10.
Use the associative property. Group the numbers differently.
(19 + 15) + 5
Instead of grouping 19 with 15, group 15 with 5 and do tat addition first.
(19 + 15) + 5 =
= 19 + (15 + 5) 15 + 5 is easy: it is 20
= 19 + 20
= 39
12.
Use the commutative property to change the order,
$9.50 + $0.50 = $10.00, so do that first.
$9.50 + $11.49 + $0.50 =
= $9.50 + $0.50 + $11.49
= $10.00 + $11.49
= $21.49
14.
Change the order and grouping using the commutative and associative properties of addition. Then -0.50 and 0.50 add to zero.
(-0.50 + 9.89) + 0.50 =
= -0.50 + 0.50 + 9.89
= 0 + 9.89
= 9.89