Amiddle school class attendance on friday was 792. this was two and three-fourths times ( 2 3/ it's a mixed number ) as many students as thursday. what was the attendance for thursday?

To do this we're going to have to divide fractions.
To divide fractions you multiply the first fraction by the reciprocal of the second fraction, which is the fraction turned upside down.

So we're going to have to convert the mixed number to a fraction, by multiplying the whole number by the denominator, then adding that to the numerator (this works for all mixed numbers)
2 x 4 + 3 = 11

The mixed fraction is 

Now set up our equation

(simplify:) 288

The answer is 288 

Hopefully this helps! If you have any more questions or don't understand, feel free to DM me, and I'll get back to you ASAP! :)

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table

Um what? rephrase that ?