Объяснение:
1)
int main()
{
int a;
float b;
cout << "enter length in centimeters ";cin >> a;
b = a / 2.5;
cout
}
2)
int main()
{
float a,b,c,d,e;
cout << "enter the number of books purchased "; cin >> a;
cout << "enter their price "; cin >> b;
cout << "enter the price of purchased notebooks "; cin>>c;
cout << "enter their price "; cin >> d;
e = a * b + c * d;
cout
}
3)
int main()
{
float a,b,c;
cout << "enter the length of the first leg "; cin >> a;
cout << "enter the length of the secomd leg "; cin >> b;
c = (a*b) / 2;
cout
}