Answer:
40
Step-by-step explanation:
Two ways we can solve this problem:
1. Graphically
2. Mathematically
Because you already solved it graphically, I will show you how to do so mathematically. Of course, graphically is much much easier and more efficient in this problem.
Let's break the problem down.
First, we are given a graph which contains a slope.
To find slope, we use the technique -> rise/run
Picking 2 obvious points from the graph, we can see 
1st point -> (10, 20) 
2nd point -> (40, 80)
Now, let's find the slope

Now, we have an equation y = 2x, where y = number of pies and x = cups of sugar
We want to find how many cups of sugar we need to bake 80 pies. Simply substitute 80 = number of pies = y
y = 2x -> 80 = 2x
Solving for x, divide both sides by 2
40 = x
We need 40 cups of sugar.
 
        
             
        
        
        
Answer:

Step-by-step explanation:
Multiply both sides by 2
2x=3y+6
Move variable to the left-hand side and change its sing
-3y=6-2x
Divide both sides of the equation by -3

 
        
                    
             
        
        
        
answer = 2
You can just use a calculator unless you need to show your work
 
        
             
        
        
        
Hey there ..
Contacted you through the comments asking for the formulas but you seem like forgot to put em ..
Will be pleased to help anytime ..
See ya