How do u do:

8/11 (n-10) = 64

Firstly multiply the 8 by (n-10)

8 (n-10) = 8n-80

form equation

(8n-80) / 11 = 64

multiply both sides by 11

8n - 80 = 64 x 11

8n - 80 = 704

than add 80 to both sides

8n - 80 + 80 = 704 + 80

8n = 784

divide both sides by 8

8n/8 = 784/8

n = 98