(MIDDLE SCHOOL MATH) (MORE THAN 5 POINTS!) HELP PLEASE

Ineed with number 6 , explain how to get 1978

He weights of 2-pound bags of best dog food are approximately normally distributed with a given mean  and standard deviation  according to the empirical rule, what percentage of the bags will have weights within 3 standard deviations of the mean? 47.5%68%95%99.7%

Fast! find the length of cu. the triangles are similar. show your work.