Question

Ce suma de bani a avut Alin daca,dupa ce a cheltuit doua optimi din ei ,apoi o patrime din rest si Inca 7 lei,constata ca i-au ramas 20 lei?

Answer 1

Rezolvarea : 
x = suma de bani avuta 
20 lei ⇒ au ramas
2/8x+1/4•2/8x+7=20
2/8x+2/32x+7=20
2/8x+1/16x+7=20 ⇒ folosim amplificarea si-l amplificam cu 2 
4/16x+1/16x+7=20
5/16x+7=20
5/16x=20-7=13
x=13:5/16=13•16/5=208/5=41,6 lei
⇒ raspunsul este : ⇒ 41 , 6 lei ( suma avuta ) 

Answer 2

x-2/8=y
y-1/4-7=20
y-1/4=20+7=27
4/4-1/4=27
1/4=27:3=90
4/4=90x4=360

8/8-2/8=360
8/8=360:2x8=1440 lei a avut

verificare
8/8-2/8=6/6
6/6=1440:8x6=1080(cheltuiti)
1440-1080=360
4/4=360
4/4-1/4=3/4
3/4=360:4x3=27
27-7=20 lei ramasi