Evaluate and then express each of the following statements as a general property of operations using letter symbols (variables). 3.1.1 (16 × 97) (16 × 3) can be calculated mentally and exactly by 16 × (97 3). (2) 3.1.2 12 cents plus 8 cents have the same value as 20 cents (2) 3.1.3 (231 198) 2 can be calculated exactly by 231 (198 2) (2) 3.1.4 (13 × 25) × 4 can be calculated mentally and exactly by 13 × (25 × 4). (2) 3.1.5 123 298 × 39 39 is an easy mental calculation. (2) 3.1.6 0 23 13 37 is an easy mental calculation. (2) 3.2 Give the name of each of the properties illustrated in 3.1.1-3.1.6