Vă rog! Exercitiul din imagine!
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Fie x suma intitiala.Atunmci el cheltuiestre

prima data

2x/5+300 rest x-(2x/5+300)=3x/5-300

a doua ora 2/3* (3x/5-300)+100=2x/5-200+100=2x/5-100

acum avem 2 variante; variabnta 1, mai rapida

noul rest este 3x/5-300-(2x/5-100)=23800

x/5-200=23800

x/5=24000

x=24000*5=120 000 suma initiala

a deoua varianta, cl;asica este sa adunam cheltuielile si restul si sa ne dea suma , noata cu x

2x/5+300 +2x/5-100+23800=x

4x/5+24000=x

24000=x-4x/5=x/5

x=24000*5=120000

notam cu s suma initiala, prima cheltuiala=2s/5+300,

bani ramasi=s-2s/5-300=3s/5-300, a doua oara cheltuie (3s/5-300)*(2/3)+100=

= (6s/15)-(600/3)+100=2s/5-200+100=2s/5-100,

s=2s/5+300+2s/5-100+23800, s=4s/5+24000 numitor comun 5

5s=2s+1500+2s-500+119000, s=119000+1000=120000