Plz help.

Which three lengths could be the lengths of the sides of a triangle? 21 cm, 7 cm, 7 cm 9 cm, 15 cm, 22 cm 13 cm, 5 cm, 18 cm 8 cm, 23 cm, 11 cm

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36

Which best describes the construction of a triangle if given the segment lengths of 2 cm, 3 cm, and 5 cm? a) unique triangle b) cannot be determined c) triangle not possible d) more than one triangle