Răspuns:
1.
int n,c,p=1;
cin>>n;
while(n)
{c=n%10;
if(c%2==1)p*=c;
n/=10;
}
cout<<p;
2.
int n,x,nr=0;
for(int i=1;i<=n;i++)
{cin>>x;
if(x>=0 and x%7==0)nr++;
}
cout<<nr;
3.formula
S+=1/(i*(i+1));
4.int n,S=0;
cin>>n;
for(int d=2;d*d<=n;d++)
if(n%d==0)S+=d+n/d;
if(d*d==n)S+=d;
cout<<S;
5.principalul
if(x>10 and x<100)S+=x;
Explicație: