There are 29 students in a classroom with 7 tables. If 4 students can sit at a table, how
many students cannot sit down at tables?

one student cannot sit down at tables

Step-by-step explanation:

There are 29 students and 7 tables 4 students can sit at each table.  7 x 4 = 28

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.