Big ! in a hall there are 2100 seats. in a row there are either 45 or 40 seats. there are three times more rows with 45 seats than with 40 seats. how many rows are there?

The construction of copying qpr is started below. the next step is to set the width of the compass to the length of ab. how does this step ensure that a new angle will be congruent to the original angle? by using compass take the measures of angle and draw the same arc according to it.