I need these done right

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

b=12

Step-by-step explanation:

9^2 + b^2 = 15^2 by the pythagorean theorem

81 + b^2 = 225

b^2 = 144

b = 12