54 
A right triangle is a shape that looks like half of a square. The height of the triangle is 12, and the base of the triangle is 9. To find the area, use the following formula: 
A = 

= 

= 

= 54 
 
 
        
             
        
        
        
Answer: correct answer is B.(2x+3y)(4x^2-6xy+9y^2)
8x^3 + 27y^3
(2x)^3+(3y)^3
(2x+3y)(4x^2-6xy+9y^2) <----answer
 
        
             
        
        
        
For everyone 4 feet he drops, 1 second will pass. (for everyone 1 second that goes by, he will be 4 feet lower)
12/3=4
        
             
        
        
        
Answer:
The first step is to replace the y in y-x=15 with 7x (we can do this because the first equation tells us that they're equal)
solve and get
(2.5,17.5)
or x= 2.5 y=17.5
Step-by-step explanation:
The first step is to recognize that y=7x which means that we can just replace the y in the second equation with 7x
7x-x=15
6x=15
x=2.5
Then we can solve for y
y=7(2.5)
y=17.5
 
        
             
        
        
        
Answer:
No, it is not a right triangle.
Step-by-step explanation:
The simplest way to determine is testing out the numbers with Pythagorian theorem. 
If it complies with the theorem, it is a right triangle.
let's assume c = 28, b = 21, and a = 20
the longest side is the hypotenuse so side c (28 in) will be the hypotenuse.
According to the Pythagorian theorem, the square of the length of hypotenuse must equal to the sum of squares of other two sides.
check:
c^2 = 28^2 = 784
a^2 + b^2 = 21^2 + 20^2 = 841
because c^2 is not equal to a^2 + b^2, the triangle is not a right triangle.