解:设这个数为x
(10x-1.8)÷2+0.26=6.86
(10x-1.8)÷2=6.6
10x-1.8=13.2
10x=15
x=1.5
算术法:
[(6.86-0.26)×2+1.8]÷10
=(6.6×2+1.8)÷10
=(13.2+1.8)÷10
=15÷10
=1.5