Answer:
There are 392 students in the seventh grade.
Step-by-step explanation:
Let us assume that there are x number of students in the seventh grade.
Now, 3/8 of the seventh grade students were taking Advanced math at the beginning of the year, but seven dropped out by the end of the year.
So, after the end of the year there were [tex](\frac{3}{8}x - 7)[/tex] number of students taking advanced math.
So, as per given condition, [tex](\frac{3}{8}x - 7) = 140[/tex]
⇒ [tex]\frac{3}{8}x = 147[/tex]
⇒ x = 392
Therefore, there are 392 students in the seventh grade. (Answer)