Need help on calculus

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

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%

Calculate the missing value. round the answer to on decimal place. start with 70, increase it by 21%, and end up with