Solve an algebraic equation with one variable
Objectives
Student will be able to:
solve addition and subtraction equations containing one variable.
use inverse operations to isolate the variable in an equation.
check solutions to addition and subtraction equations with one variable.
Introduction
Sasha is 2 years older than her brother. If Sasha is 11, how old is her brother?
You can answer the problem by solving the equation
An
equation
states that two quantities are equal using an equal sign.
A
variable
is a letter or symbol that represents an unknown number.
For example,
x
is the variable in the equation
Solving an equation
means finding the value that makes the statement true.
To do this, isolate the variable on one side of the equation by performing the
inverse operation
. Addition and subtraction are inverse operations.
Solve
Step 1: Decide which operation will isolate the variable.
Since this is an addition equation, the operation to isolate is subtraction.
Step 2 : Use subtraction to solve.
Step 3: Check your solution by replacing
x
with 9 in the original equation.
Both sides are the same.
The solution is
Sasha's brother is 9 years old.
Examples
1.
Solve for
x.
Step 1: Decide which operation will isolate the variable.
Since this is a subtraction equation, the operation used to isolate the variable is addition.
Step 2: Isolate the variable.
Add 15 to both sides.
Step 3 : Check your solution by replacing
x
with 33 in the original equation.
Both sides are the same, so the solution is correct.
2.
Rashad scored 8 points higher than his friend on the math test. If Rashad scored 94 points, how many points did his friend score?
Solve for
p
:
Check your solution.
So, Rashad's friend scored 86 points.
Try Together
Complete the exercises.
1.
Solve and check.
2.
Solve and check.
Please evaluate the student's answers:
Excellent
Good
Okay