The document discusses internal and external angles of a triangle. It presents a triangle diagram labeled with angles A, B, and C. It asks what the measure of angle B is and what the measure of angle A is. The solutions provided are that the measure of angle B is 90 degrees and the measure of angle A is 45 degrees. The document was done by Gonçalo Pereira at ESCOLA B2.3 DE AZEITAO in Portugal.