Answer:
20d + 30d
Step-by-step explanation:
20 and 30 minutes per day
 
        
                    
             
        
        
        
Answer:
f(x) - when referring to a function - means that x is the input value that you substitute into an equation. 
For example, if f(x) = 2x + 3 and you were asked to find f(2), you could substitute x = 2 into the equation 2x + 3 to get 7.
Hope this helps!
 
        
             
        
        
        
Answer:
A
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
BC² = 9² + 12² = 81 + 144 = 225 ( take the square root of both sides )
BC =  = 15 → A
 = 15 → A