Question

Buna seara as avea nevoie de un raspuns la exercitiul:
{[(7a-5)+2×6] :4+5}×10-[(4+6)×5-42]=112

Answer 1

{[(7a-5)+2×6] :4+5}×10-(10x5-42)=112
{[(7a-5)+2×6] :4+5}×10-8=112
{[(7a-5)+2×6] :4+5}×10=120
(7a-5+12):4+5=12
(7a-5+12):4=7
7a-5+12=28
7a-5=16
7a=21 => a=3

Answer 2

se rezolva retrograd, (de la coada la capat) prin operatii inverse:
{[(7a-5)+2×6] :4+5}×10-(10x5-42)=112
{[(7a-5)+2×6] :4+5}×10-8=112
{[(7a-5)+2×6] :4+5}×10=112+8
{[(7a-5)+2×6] :4+5}×10=120
{[(7a-5)+2×6] :4+5}=120:10
(7a-5+12):4+5=12
(7a-5+12):4=12-5
(7a-5+12):4=7
(7a-5+12)=7x4
7a-5+12=28
7a-5=28-12
7a-5=16
7a=16+5
7a=21
 a=21:7
 a=3