Erica used friendly numbers to find 43-19 she added 1 to 19 and subtracted 1 from 43 what is erica's error

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?

Factor the expression using the gcf. the expression 21m−49n factored using the gcf

Does anyone know how to solve and graph this: 4 + | a + 2 | < 7the only part i don't get is the "4 +"