Answer:
C. Infinite solutions
Step-by-step explanation:
I'll use the equal value method and make the second equation equal 6 instead of 18, so I have to divide the entire equation by 3
(6x+15y=18)/3 = 2x +5y = 6
The second equation is the same thing as the first one, meaning no matter what value they will equal the same thing, also meaning there are infinite solutions
Given:
The number of sides of given polygon = 4
To find the sum of the interior angles of the polygon.
Formula
The sum of interior angles of any polygon is

where, n be the number of sides of the polygon.
Now,
Taking n = 4 we get,

or, 
or, 
Hence,
The sum of the interior angles of the polygon is 360°.
The answer is a chemical reaction
Since addition is commutative, she can add anyway she wants.
(17+51)+(10+13)
(51+10)+(17+13)
Hope this helps.
Expression 1 is 25
6*7-3^2*9+4^3
First simplify all the exponents to get 6*7 - 9 * 9 + 64 and then multiply the two numbers to get 42 - 81 + 64 and just add = 25
For expression 2, if you put the parantheses around (5+4)*2+6-2*2-1, it'll be 19
(5+4)*2+6-2*2-1
9*2+6-2*2-1
18+6-4-1
24-5
19
Remember order of operations