Answer:
3*(5*x-7)-(15*x-21)=0 
Step-by-step explanation:
3 • (5x - 7) -  (15x - 21)  = 0 
Step  2  :
Equation at the end of step  2  :
  0  = 0 
Step  3  :
Equations which are always true :
 
        
             
        
        
        
Step-by-step explanation:
the total surface area is the sum of the individual areas.
we have the ground area : a 6×6 square. = 36 cm²
and we have 4 equal triangles. 
the area of a triangle is baseline × height / 2.
which is for each of these triangles
6 × 12 / 2 = 3 × 12 = 36 cm²
so, the total surface area of the pyramid is
36 + 4×36 = 5×36 = 180 cm²
 
        
                    
             
        
        
        
Answer: A
Step-by-step explanation: you would multiply
 
        
             
        
        
        
Step-by-step explanation:
there is 3 feet in a yard 
divide by 3
18 ÷ 3 = 6
true