递等式（能巧算就巧算）①26×20.2-8.4-1.8 ②（3.2×0.4-0.68）÷0.25×4

① 26×20.2-8.4-1.8
= 26 X 2 X 10.1 -（8.4 + 1.8）
= 52 X 10.1 - 10.2
= 52.52- 10.2
= 42.32
②（3.2×0.4 - 0.68）÷0.25 × 4
=（3.2×0.4 - 0.68）÷（1/4）× 4
=（3.2×0.4 - 0.68）× 4 × 4
=（1.28 - 0.68）× 4 × 4
= 0.6 X 16
= 9.6