What is the reciprocal of -7/9?

Se tiene en una caja de canicas 10, 4 blancas y 6 negras ¿cual es la probabilidad que en 2 extracciones con reemplazo sean blancas? ¿cual es la probalidad que en 2 extracciones sin reemplazo sean negras?

If using the method of completing the square to solve the quadratic equation x 2 + 16 x + 24 = 0 x 2 +16x+24=0, which number would have to be added to "complete the square"?

Maria has $10,000 to invest in two accounts. he decides to invest one part in an account with 5% interest and the rest in an account with 8% interest. at the end of the year he has earned $702,50 in interest.¿how much did maria invest in the 8% account?