Fie x=numarul cautat
1/4*X=X/4- in prima zi
3x/12-in a doua zi
x-x/4=4x/4-x/4=3x/4 in a treia zi
50 km- in a patra zi
x/4+3x/12+3x/4+50/1=x/1
3x/12+3x/12+9x/12+600/12=12x/12/ imparim prin 12 si ⇒
⇒3x+3x+9x+600=12x
18x+600=12x
18x-12x=600
6x=600/6
x=100
Serban a cheltuit in cele 4 zile de vacanta 100 lei
2)
Fie x=numarul sandalelor
Fie y=numarul pantofilor
x=3*y=3y
x+3y=20010
x+y=270+524
x+y=794/*(-1)
x+3y=20010
-x-y=-794
x+3y=20010
2y=19216/2
y=9608
x+9608=794
x=9608-794
x=8814