What is the answer of t - 12 = 11

When you answer this can you explain

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%

Secant be and cf intersect at point d inside a what is the measure of cde