Răspuns :
(a+a+1+a+2+a+3+a+4):21=9r6
5xa+10=21x9+9
5a+10=189+9
5a+10=198
5a=198-10
5a=188
a=188:5
a=37r3
5xa+10=21x9+9
5a+10=189+9
5a+10=198
5a=198-10
5a=188
a=188:5
a=37r3
(a+b+c+d+e):21=9 rest 6
a+(a+1)+(a+2)+(a+3)+(a+4)=21*9+6
5a+10=189+6
5a+10=195
5a=195-10
5a=185
a=185:5
a=37
=>a=37
b=37+1=38
c=37+2=39
d=37+3=40
e=37+4=41
(a+b+c+d+e):21=9 rest 6
(37+38+39+40+41):21=9 rest 6
195:21= 9 rest 6.....pentru ca : 195=(21*9)+6
=189+6
=195
a+(a+1)+(a+2)+(a+3)+(a+4)=21*9+6
5a+10=189+6
5a+10=195
5a=195-10
5a=185
a=185:5
a=37
=>a=37
b=37+1=38
c=37+2=39
d=37+3=40
e=37+4=41
(a+b+c+d+e):21=9 rest 6
(37+38+39+40+41):21=9 rest 6
195:21= 9 rest 6.....pentru ca : 195=(21*9)+6
=189+6
=195