Start with the equation with the fewest variables, .

Solve for by dividing both sides of the equaion by 6:

Plug this  value into the second equation to solve for :

Subtract 10 from both sides:

Divide by 9:

Plug these and values into the first equation to find :

Combine like terms:

Subtract 2:

Divide by -4:

Therefore the final solution is .

 and  add up to 16:

When  is doubled to , they sum to 34:

We have two equations and two unknowns, so we can find a solution to this system.

Solve for in the first equation:

Plug this into the second equation:

Solve for :

Use this  value to find . We already have a very simple equation for , .

Therefore the answer is .

For the second equation, solve for  in terms of .

Plug this value of y into the first equation.

rearranges to

and

, so

In the second equation, you can substitute  for  from the first.

Now, substitute 2 for  in the first equation:

The solution is 

To find the point where these two lines intersect, set the equations equal to each other, such that  is substituted with the  side of the second equation. Solving this new equation for  will give the -coordinate of the point of intersection.

Subtract from both sides.

Divide both sides by 2.

Now substitute  into either equation to find the -coordinate of the point of intersection.

With both coordinates, we know the point of intersection is . One can plug in  for  and  for  in both equations to verify that this is correct.

Add the equations together.

Put the terms together to see that .

Substitute this value into one of the original equaitons and solve for .

Now we know that , thus we can find the sum of and .

We can solve this problem by setting up a simple system of equations. First, we want to change the equations so one variable can cancel out. Multiplying the first equation by 2 and the second equation by 3 gives us a new system of  and . These equations add up to  or . Plugging in 7 for  in either of the original two equations shows us that  is equal to 1 and the point is .

This system has infinite solutions becasue the two equations are actually the exact same line. To discover this, put both equations in terms of y.

First, . Add y to both sides:

Now add 3 to both sides:

Now we can show that the second equation also represents the line

add 6 to both sides

divide both sides by 2

Since both equations are the same line, literally any point on one line will also be on the other - infinite solutions.

A system of equations can be solved by subsituting one variable for another. Since we know that , we can subsitute this into the other equation so . This expression can be solved to find that . Now that we know the value of  it can be subsituted into either of the original equations to find .