(2) 5.4÷(3.94+0.86) ×0.8=5.4×0.8÷4.8=0.9

(5) 12.5÷25=0.5

( 12.5+7.5)÷25=0.8

0.8-0.5=0.3

(6)50×65×6÷(65-50)= 1300

s =( 13+ 13+8)×50÷2 = 850

1 1900÷850= 14

65438+1October 26

(5)2n, 2n- 1(0 is not a natural number)

(6)0,2,2