13.
x=suma initiala
4x/6=2x/3 =pret minge
x-2x/3=x/3 =rest
(x/3+6)2/3=2x/9+4 =pret carte
2x/3+2x/9+4+8=x+6
6x+2x+108=9x+54
x=54 lei
12.
|-------|-------|-------|------| PRIMA ZI
1/4
|----|-----|-----|-----| a 2 a zi
1/4
|-----|-----|-----| a 3a zi
1/3 +72
a treia zi 72:2x3 = 108 lei ( a cheltuit 1/3= 108:3=36)
a doua zi 108:3x4= 144 lei ( a chetuit 1/4= 144:4=36)
prima zi 144:3x4=192 lei ( a cheltuit 1/4= 48 lei)
14.|-----|-----|-----|-----|-----|
13+3+4=20(4/5 sau 4 seg.din cele 5)
20÷4=5 (1/5 sau 1 seg. din cele 5)
5+4=9 prune ia Maria
5+3=8 prune ia Radu
9+8+13=30
