The trapezoid $ABCD$ satisfies $AB \parallel CD$, $AB = 70$, $AD = 32$ and $BC = 49$. We also know that $\angle ABC = 3 \angle ADC$. How long is the base $CD$?
Problem
Source: 2021 Dürer Math Competition Finals Day2 E13 https://artofproblemsolving.com/community/c2749870
Tags: geometry, trapezoid, equal angles