If y varies directly with x, and y = 6 when x = 9, find the value of x when y = 7

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.