un proicet =100*35=3500zile elev
fie x , numarulde zile in care lucreaza 4+77 elevi
atunci
35*(4+x) +(35+77)*x=3500
35*4+35x+112x=35*100
147x=35*100-35*4
147x=35*96
21x=5*96
7x=5*32
x=5*32/7≈22,86zile
4+22,86≈26,86≈27zile ca sa fie intreg
altfel
fie x numarulde zile lucrate in total atunci
35*x+112(x-4)=3500
35x+112x=3500+112*4
147x=3948
x=3948:147
x=26,86≈27 zile