How many ways are there to list the digits {1,2,2,3,4,5,6} so that identical digits are not in consecutive position?

Which triangle congruence postulate or theorem justifies my claim that the steps i made using construction paper and scissors produce an isosceles triangle? was it sss, sas, asa, aas, or hl?

Pls! does anybody know a shortcut for answering these types of questions in the future?

Estimate the area under the curve f(x) = 16 - x^2 from x = 0 to x = 3 by using three inscribed (under the curve) rectangles. answer to the nearest integer.