i think you answer would be b "omg all the b's xD"  I MIGHT BE WRONG THO and if i am in suuuper sorry :/
 
        
             
        
        
        
Answer:
Step-by-step explanation:
Given the Total revenue R(x) = 2x
Cost C(x) = 0.01x²+0.3x+30 where;
x = 30 and dx/dt = 9units per day.
Rate of change of revenue dR/dt = dR/dx • dx/dt
dR/dt = 2dx/dt
dR/dt = 2(9) = $18
Rate of change of revenue with respect to time is 18dollars/day.
Rate of change of cost dC/dt = dC/dx • dx/dt
dC/dt = (0.02x+0.3)dx/dt
dC/dt at x = 30 and dx/dt = 9 will give;
dC/dt = {0.02(30)+0.3}×9
dC/dt = (0.6+0.3) × 9
dC/dt = 0.9×9
dC/dt = $8.1
Rate of change of cost with respect to time is 8.1dollars/day
Profit = Revenue - Cost
Profit = 18-8.1
Daily Profit = $9.9
 
        
             
        
        
        
Answer:
Equation shown 
Step-by-step explanation:
Eq(1): x-3y=-12
 X=-12+3y
 =-4+y
Eq(2): x-3y=-6
 X=-6+3y
 =-2+y
 
        
                    
             
        
        
        
I have a shout out for a couple days I can get you the phone case I have a lot to
        
             
        
        
        
So, first turn your fractions into decimals. ⅞ = 0.875 which rounded is 0.88. 4/5 = 0.8. Next, put the decimals into the equation to replace the fractions. 0.88 + 4.2 - 0.8. Next solve the problem. So 0.88 + 4.2 = 5.08. Now your equation should look like this 5.08 - 0.8. Then subtract 0.8 from 5.08 which gives you 4.28. So 4.28 is your answer.