What is 0.78 * 4 / 13 + (11 and 18 / 29-2 / 51) * (0.8-4 / 5)

What is 0.78 * 4 / 13 + (11 and 18 / 29-2 / 51) * (0.8-4 / 5)

0.78 * 4 / 13 + (11 and 18 / 29-2 / 51) * (0.8-4 / 5)
=39/50×4/13+0
=6/25

What is 1 / 1 * 1 / 3 + 1 / 3 * 1 / 5 + 1 / 5 * 1 / 7 +. 1 / 49 * 1 / 51,

1 / 1 * 1 / 3 + 1 / 3 * 1 / 5 + 1 / 5 * 1 / 7 +. + 1 / 49 * 1 / 51 +... + 1 / (2n-1) (2n + 1) = 1 / 2 [1 / 1-1 / 3 + 1 / 3-1 / 5 + 1 / 5-1 / 7 +. + 1 / 49-1 / 51 +... + 1 / (2n-1) - 1 / (2n + 1)] = 1 / 2 [1-1 / (2n + 1)] = n / (2n + 1) when n = 25, 1 / 1 * 1 / 3 + 1 / 3 * 1 / 5 + 1 / 5 * 1 / 7 +. + 1 / 49 * 1 / 51 +... + 1 / (2n-1) (...)

What is (- 15) divided by (- 6 / 25) multiplied by 6

(- 15) divided by (- 6 / 25) multiplied by 6 is equal to (- 15) multiplied by (- 6 / 25) multiplied by 6 = 108 / 5