Answer:
r can be any number -1.5 to 9.4999999
Step-by-step explanation:
 
        
             
        
        
        
Answer:
   A: 244 pounds
   B: 122 pounds
   C: 274 pounds
Step-by-step explanation:
We have A+B+C = 640; A=2B; C=A+30. Substituting the last into the first gives ...
   A + B + (A +30) = 640
   2A +B = 610 . . . . . . . . . . . . subtract 30
Substituting the second into this equation gives ...
   2(2B) +B = 610
   B = 610/5 = 122 . . . . . divide by 5
   A = 2B = 244 . . . . . . . .find A from B
   C = A+30 = 274 . . . . . find C from A
Box A weighs 244 pounds; box B weighs 122 pounds; box C weighs 274 pounds.
 
        
             
        
        
        
B, x=12 because 140-80=60, 60/5=12
        
             
        
        
        
C^2=a^2+b^2  we are given the hypotenuse of 19 units and one leg of 8 units so:
19^2=8^2+b^2
361=64+b^2
b^2=297
b=√297
b≈17.2 to the nearest tenth