Question

Un elev are o suma de bani.Dupa ce dubleaza aceasta suma, cheltuieste 15 lei.Dubleaza apoi suma ramasa si mai cheltuieste 20 lei.Dupa ce dubleaza noul rest si cheltuieste inca 25 lei, elevul constata ca i-au ramas 50 lei.Ce suma a avut la inceput?

Answer 1

a-suma de bani

2x[2x(2xa-15)-20]-25=50
2x[2x(2xa-15)-20]=75
2x(2xa-15)-20=75:2
2x(2xa-15)=75:2+20
4xa-30=75:2+40:2
4xa-30=115:2
4xa=115:2+30
4xa=115:2+60:2
4xa=175:2
a=175:8
a=21,875 lei

Answer 2

a- suma de bani
((ax2-15)x2-20)x2-25=50
(ax2-15)x2-20)x2=50+25
                            =75
((ax2-15)x2-20)=75:2
                         =37,5
(ax2-15)x2=37,5+20
                 =57,5
ax2-15=57,5:2
           =28,75
ax2=28,75+15
ax2=43,75
a=43,75:2
a=21,875 lei a avut la inceput