Hello !
You have to do as follow :

<h2><u><em>Divide and subtract from both sides</em></u></h2>
Answer:
The number of students that bring their lunches is 12
Step-by-step explanation:
Let
x -----> the number of students that bring their lunches
y -----> the total number of students in a class
we know that
The number of students that bring their lunches divided by the total number of students in a class must be equal to 3/8
-----> equation A
-----> equation B
substitute the value of y in equation A and solve for x
therefore
The number of students that bring their lunches is 12
Answer:
30?
Step-by-step explanation:
divide 20 by 8 and then times the answer by 12