https://pt-pt.khanacademy.org/math/pre-algebra/pre-algebra-math-reasoning/pre-algebra-number-patterns/v/math-patterns-example-1
Clique na hiperligação https://pt-pt.khanacademy.org/math/pre-algebra/pre-algebra-math-reasoning/pre-algebra-number-patterns/v/math-patterns-example-1 para abrir o URL.