(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