The easy thing to do is eliminate x by subtraction 
 
   x + 7y = 24
- x - 9y = -24
-------------------
      16y = 48
now solve for y and then substitute the value into either original equation to find x
        
             
        
        
        
The first expression can be simplified by combining like terms.
First, the terms "4b" and "-3b" can be combined to form "b"
Then, the terms "-7" and "9" can be combined to form "2"
Finally, we simply put these two final terms together, to form "b+2"
Hence, 4b-7-3b+9 is equal to be + 2.
Hope this helps!
        
             
        
        
        
4)
the arrow touches the ground when the heigth is 0
so we need to replace h=0 and solve for t

<em>the arrow tuches the ground at 3.4 seconds</em>
5)

replacing

<em>solve for m</em>

<em>the mass is 13.50Kg</em>
<em />
 
        
             
        
        
        
we are given 

where 
price p( in dollars) of a new smartphone 
t is the number of months since January
now, we can solve for t
step-1:
Add both sides by 4t^2


step-2:
Subtract both sides by p


step-3:
divide both sides by 4



step-4:
Take sqrt both sides 


so, we get 
 ..............Answer
..............Answer