Ms jenkins was arranging chairs for school awards assembly each row contained 15 chairs if there were 21 rows how many chairs had to be arranged

The answer would be 21 times 15. So there would be 315 chairs in total.

315 chairs had to be arranged

We know that because if each row has 15 chairs and there’s 21 rows then all you do is multiply 15 by 21 which gets you 315

One unique triangle, because those angles add up to 180, and that's how many degrees there are in one triangle.