I need answer soon! If 70 + m + n - 20 = 80 and m = 2n, then what is the value of n?

It'd be great if there was an explanation, but I'm not too picky...

Iq scores for adults age 20 to 34 years are normally distributed according to n(120, 20). in what range does the middle 68% of people in this group score on the test?

Mr. roseanne will buy 12 1/2 pounds beef for for a cookout. the price for the first 3 pounds of beef is $4.99 per pound. after that, the price is $4.49 per pound. how much will mr.roshan pay for the beef

Jocelyn estimates that a piece of wood measures 5.5 cm. if it actually measures 5.62 cm, what is the percent error of jocelyn’s estimate? a. 2.13% b. 2.18% c. 12%