To solve a system of equations by substitution, follow these steps in order:
Step 1: Solve one equation for one variable in terms of the other variable.
For example, let's solve the second equation for x:
x - 2y = 11
-> x = 2y + 11
Step 2: Substitute the expression obtained in Step 1 into the other equation.
Substitute the expression 2y + 11 for x in the first equation:
-7x - 2y = -13
-> -7(2y + 11) - 2y = -13
Step 3: Simplify and solve the resulting equation for the remaining variable.
Expand and solve the equation:
-14y - 77 - 2y = -13
-> -16y - 77 = -13
-> -16y = 64
-> y = -4
Step 4: Substitute the value of y obtained in Step 3 into either equation to solve for the other variable.
Using the second equation:
x - 2y = 11
-> x - 2(-4) = 11
-> x + 8 = 11
-> x = 3
Step 5: Check your solution by substituting the values of x and y into both original equations.
Substituting x = 3 and y = -4 into the first equation:
-7x - 2y = -13
-> - (7 * 3) - (2 * -4) = -13
-> -21 + 8 = -13
-> -13 = -13
Substituting x = 3 and y = -4 into the second equation:
x - 2y = 11
-> 3 - 2(-4) = 11
-> 3 + 8 = 11
-> 11 = 11
Both equations are satisfied, so the solution to the system of equations is x = 3 and y = -4.