{4/15 : (+ 4/25) - [.....continua...
{4/15 * (+ 25/4) - [.... continua...
{ 5/3 - [ (+ 9/25) - 3/5 * (5/15 - 3/15)] :(4/25)}: .... continua...
{5/3 - [9/25 - 3/5 * 2/15 ] * 25/4} : [ 4/13 * (4/12 + 3/12 + 6/12) - (3/2 + 2/2) *
* (5/10 - 2/10)] =
= {5/3 - [9/25 - 6/75] * 25/4} : [4/13 * 13/12 - 5/2 * 3/10] =
= {5/3 - [27/75 - 6/75] * 25/4} : [ 1/3 - 3/4] =
= { 5/3 - 21/75 * 25/4 } : [4/12 - 9/12] =
= {5/3 - 7/4} : [- 5/12] =
= {20/12 - 21/12} * [ - 12/5] =
= {- 1/12} * [- 12/5] = + 1/5.
Ciao @sara_wgf_uvu