Write the sum of first n natural numbers.

The sum of the first n natural number = n * (n+1) / 2, for n a natural number.

For example, you want to calculate the sum and average of any five numbers entered by the user. i.e., If you want to calculate the sum and average or percentage of multiple user-entered numbers, then please refer to the following program.

mr. flanders’ class sold 47 doughnuts and   mr. rodriquez’s class sold 38 cartons of milk

step-by-step explanation:

let x be the number of doughnuts sold by mr. flanders’ class and y be the number of cartons sold by mr. rodriquez’s class.

1. together, the classes sold 85 items, then

x+y=85.

2. both classes earn earned $104.49 for their school. if doughnuts were sold for $1.35 each, then x doughnuts costed $1.35x. if cartons of milk were sold for $1.08 each, then y cartons costed $1.08y. hence,

1.35x+1.08y=104.49.

3. solve the system of two equations: