If the ratio of students who are buying lunch to those who bought their lunch are 3:1. This means that for every 3 students that buy their lunch, there is 1 student who brings their lunch. This allows us to create the following equation:
3x + 1x = 136
To solve this equation, we must first combine like terms on the left side of the equation, which gives us:
4x = 136
Finally, we should divide both sides of the equation by the coefficient of the variable x, which is 4:
x = 34
We know that the number of students that brought their lunch is represented by the expression 1x. Therefore, 34(1), or 34 students brought their lunch.
Hope this helps! :)