For this case we have the following system of equations:

To solve, we clear "x" from the second equation:

We substitute "x" in the first equation:

We clear the value of the variable "y":

We look for the value of the variable "x":

Thus, the solution of the system is given by:

Answer:

Option D
The third one because 2(15+5)=2(20)=40
Volume of a Cone. The volume of a cone is 1 3 π r 2 h \frac { 1 } { 3 } \pi r ^{ 2 } h 31πr2h, where r denotes the radius of the base of the cone, and h denotes the height of the cone.
4.05-2.74=1.31
The difference is 1.31 pounds.
Yes because the solution can either be equal to 9 or less than 9 and 9=9 and 0<9 so they can both be solutions