Question

(2/5-3/20)-(9/10-4/5)=

Answer 1

..........=( 0,4-0,15)-(0,9-0,8)=0,25-0,1=0,15

Answer 2

(2/5 - 3/20) - (9/10 - 4/5) = 3/20
1) 2/5 - 3/20 = 8/20 - 3/20 = 5/20 = 1/4
2) 9/10 - 4/5 = 9/10 - 8/10 = 1/10
3) 1/4 - 1/10 = 5/20 - 2/20 = 3/20