What is the solution [tex]\((a, c)\)[/tex] to this system of linear equations?

[tex]\[
\begin{array}{r}
2a - 3c = -6 \\
a + 2c = 11
\end{array}
\][/tex]

A. [tex]\(\left(-\frac{76}{7}, \frac{17}{7}\right)\)[/tex]
B. [tex]\((3, -4)\)[/tex]
C. [tex]\((3, 4)\)[/tex]
D. [tex]\(\left(\frac{87}{7}, -\frac{5}{7}\right)\)[/tex]



Answer :

To solve the system of equations:
[tex]\[ \begin{cases} 2a - 3c = -6 \\ a + 2c = 11 \end{cases} \][/tex]

we can use the method of substitution or elimination. Here, we'll use the elimination method to find the values of [tex]\(a\)[/tex] and [tex]\(c\)[/tex].

1. First Equation: [tex]\(2a - 3c = -6\)[/tex]
2. Second Equation: [tex]\(a + 2c = 11\)[/tex]

### Step-by-Step Solution:

Step 1: Align the coefficients
We have:
[tex]\[ 2a - 3c = -6 \tag{1} \][/tex]
[tex]\[ a + 2c = 11 \tag{2} \][/tex]

Step 2: Eliminate one of the variables
To eliminate [tex]\(a\)[/tex], we can manipulate the equations to have the same coefficient for [tex]\(a\)[/tex]. Let's multiply Equation (2) by 2:

[tex]\[ 2(a + 2c) = 2 \cdot 11 \][/tex]
[tex]\[ 2a + 4c = 22 \tag{3} \][/tex]

Now our system of equations looks like:
[tex]\[ 2a - 3c = -6 \tag{1} \][/tex]
[tex]\[ 2a + 4c = 22 \tag{3} \][/tex]

Step 3: Subtract one equation from the other
Next, subtract Equation (1) from Equation (3):
[tex]\[ (2a + 4c) - (2a - 3c) = 22 - (-6) \][/tex]
[tex]\[ 2a + 4c - 2a + 3c = 22 + 6 \][/tex]
[tex]\[ 7c = 28 \][/tex]

Step 4: Solve for [tex]\(c\)[/tex]
[tex]\[ c = \frac{28}{7} = 4 \][/tex]

Step 5: Substitute [tex]\(c\)[/tex] back into one of the original equations
Now that we have [tex]\(c = 4\)[/tex], we substitute it back into Equation (2):
[tex]\[ a + 2c = 11 \][/tex]
[tex]\[ a + 2 \cdot 4 = 11 \][/tex]
[tex]\[ a + 8 = 11 \][/tex]
[tex]\[ a = 11 - 8 \][/tex]
[tex]\[ a = 3 \][/tex]

Step 6: Form the solution pair [tex]\((a, c)\)[/tex]
Thus, the solution to the system of equations is:
[tex]\[ (a, c) = (3, 4) \][/tex]

### Conclusion:

The correct choice from the options presented is:
[tex]\((3, 4)\)[/tex]

So the solution [tex]\((a, c)\)[/tex] to the system of linear equations:
[tex]\[ \begin{cases} 2a - 3c = -6 \\ a + 2c = 11 \end{cases} \][/tex]
is:
[tex]\((a, c) = (3, 4)\)[/tex].