Answer:
13. 20 + (-15) = 5 -- in total he kept 5 pounds
14. -28 + 38 = 10 -- the temperature changed by 10º over 12 hours
15. 100 + (-72) + 48 = 76
Step-by-step explanation:
13. since he gained 20lbs, then lost 15, add -15 to 20 to get 5, the amount of pounds he kept on him
14. the temperature starts at -28º then goes up 38º, so add 38 to -28.
15. the ramp goes up 100, (+100) then down 72, (-72) and then up another 48 (+48) as equation this would be 100 + (-72) + 48
