Answer:
x = 7
y = 11
Step-by-step explanation:
Given the system;
y = 2x - 3
x + y = 18
1. Approach
The easiest way to solve this system of equations is to solve the second equation for the variable (y). Then add the systems, use algebra to solve for the value of (x), then substitute that value back into one of the original equations to solve for the value of (y). Another name for the method in use is the method of elimination, this is when a [erspm manipulates one of the equations in a system of the equation such that when they add the equations, one of the variables eliminatates. Thus, they can solve for the other variable and the backsolve for the value of the unknown variable.
2. Solve one of the equations for a variable
Manipulate the system such that each equation is solved for the same variable,
x + y = 18
Inverse operations,
x + y = 18
-18 -18
x + y - 18 = 0
-y -y
x - 18 = -y
3. Use elimination
Now substitute this back into the original system,
y = 2x - 3
-y = x - 18
Add the systems,
y = 2x - 3
-y = x - 18
_________
0 = 3x - 21
Inverse operations,
0 = 3x - 21
+21 +21
21 = 3x
/3 /3
7 = x
4. Find the value of the unknown variable
Backsovle to find the value of (y),
x + y = 18
Substitute,
7 + y = 18
Inverse operations,
7 + y = 18
-7 -7
y = 11
