Y = mx + b. Use this equation for most linear functions. Enter the information that is given to you. 

Multiply the -3 and 4 to get 12.

Now divide the -12 from both sides.

-12 cancels out on the right side and your left with 

Now re-enter the info back into the formula.

Then you've got your formula
 
        
        
        
The direct variation between x and y may be written as,
                                    y = kx
where k is the constant of variation. From the first set of values of the variables,
                                 12 = k(8)
the value of k is 1.5. Substituting the next set to the same equation,
                                 y = 1.5(14) 
The value of y is 21. 
        
             
        
        
        
Just plug in 4 for the x
2*4 +4y =36
8+4y =36
4y =36-8
4y=28
y= 28/4
y=7
        
                    
             
        
        
        
Treat it as a fraction where it must stay equal
6/54
with fractions, you can do anything as long as you do it so top and bottom
so 6/54=1/9=2/18=3/27=4/36=5/45 etc
but don't forget to convert back to ratios
so some examples are 1:9
2:18
3:27
4:35
5:45
        
             
        
        
        
Answer:
The final balance is $851.11.
The total compound interest is $251.11.
Step-by-step explanation: