Question

On Sunday, a local hamburger shop sold a combined total of 320 hamburgers and cheeseburgers. The number of cheeseburgers sold was three times the number of hamburgers sold. How many hamburgers were sold on Sunday?

Answer 1

80

Explanation:

1) if the number of hamburgers is 'h', number of cheesburgers is 'c', then

2) the condition 'The number of cheeseburgers sold was three times the number of hamburgers' can be written as c=3h. Also

3) the condition 'combined total of 320' can be written as h+c=320, then

4) it is possible to make up the system of equations:

`\left \{ {{c=3h} \atop {c+h=320}} \right. \ = > \ \left \{ {{c=240} \atop {h=80}} \right.`

5) finally, number of hamburgers is 80.