x=suma initiala
2x=dubleaza suma
2x-5=cheltuie 5 lei
(2x-5)×2=4x-10 =dubleaza suma
4x-10-4=4x-14=cheltuie 4 lei
4x-14-(4x-14) × 1/4-6=96
4x-14-x+14/4-6=96
3x=116-14/4
12x=464-14
12x=450
x=37,5 lei
verificare
37,5 x2=75
75-5=70
70x2=140
140-4=136
136× 1/4=34
136-34-6=96 lei rest