Answer:
1.     second  
Step-by-step explanation:
is this like a test or sum
 
        
                    
             
        
        
        
Answer:
The answer to your question is
x = -2 and y = 10     or   x = 10 and y = -2
Step-by-step explanation:
           x + y = 8   (1)      from (1)    x = 8 - y
          xy = - 20    (2)
         
Solve them by substitution 
       (8 - y) y = - 20
       8y - y² = -20
       y² - 8y - 20 = 0
    ( y - 10) (y + 2) = 0
     y - 10 = 0              and      y + 2 = 0
    <u> y1 = 10 </u>                               <u>y2 = -2</u>
  x1 = 8 - 10                             x2 = 8 - -2
  <u>x1 = -2</u>                                  <u> x2 = 10</u>
 
        
             
        
        
        
Answer:
Below.
Step-by-step explanation:
15y + 12x = 18 
5y + 4x = 6
The  second equations is the first times 3 so they are basically the same.
Infinite Solutions.
2x+ 3y= 12 
-6y= 4x-24          Rearranging the second equation:
-4x - 6y = -24      Multiplying the first equation by 2:
 4x + 6y = 24       
- we see that the last equation is -1 * previous equation.
So there are infinite solutions.
 
        
             
        
        
        
Answer 28. 
Possible values for the three factors of -3
- 1, -1 and 3 
- -1.5, 1 and 2
- 1.5, -1 and 2  
- 1.5, 1 and -2 
Answer 29. 
The product of two nonzero integers will be less than or equal to both of the integers if they are multiplied by number itself and one or by number itself and one with negative sign.
Answer 30. 
The sign of the product of three integers with the same sign will be positive or negative. If odd number of same sign is multiplied, the product will be of that sign.
(+)  (+)  (+) = (+)
(-)  (-)  (-) =  (-)
 
        
             
        
        
        
Let p and w represent the speed of the plane and the speed of the wind, respectively.
.. speed = distance/time
.. p +w = 720/3 = 240
.. p -w = 720/4 = 180
Add the two equations to eliminate w.
.. 2p = 420
.. p = 210
.. w = p -180 = 30
The speed of the wind is 30 mph.
The speed of the plane in still air is 210 mph.