fie c, numarulde copii
atunci
c=5x+3
c=4y+2
c=7z+5
c+2=5x+3+2=5x+5=5p...5| (c+2)
c+2=4y+2+2=4y+4=4q....4| (c+2)
c+2=7y+5+2=7y+7=7r.....7|(c+2)
deci[4,5,7] |(c+2)
140|(c+2)
c+2=140k
c=140k-2, k∈N
in gradinita pot fi 140-2=138 copii sau 280-2=278copii sau 420-2=418copii sau nr mai mari
convine doar 278 copii