6th Grade Math Textbook, Fundamentals

x  1176 9117

 &KDSWHU

Solve: x(5)  12

x(5) (5) 12 (5)

x 17

Subtract 5 from

both sides to

isolate x.

2-4

1

Update your skills. See page 409 VI.

Solve Addition Equations

Objective To apply the Subtraction Property of Equality to solve algebraic addition equations

with integers • To combine numerical terms to simplify addition equations with integers

If Baltimore’s Fort McHenry Tunnel were

1176 feet longer, it would be as long as

New York’s Brooklyn Battery Tunnel.

The Brooklyn Battery Tunnel is 9117 feet long.

How long is the Fort McHenry Tunnel?

To find the length of the Fort McHenry Tunnel,

write and solve an.

Let xthe length of the Fort McHenry Tunnel.

Fort McHenry 1176 feet Brooklyn Battery

Tunnel (ft) longer Tunnel (ft)

x  1176  9117

Use the to solve an

addition equation. Addition and subtraction are inverse

operations because they “undo” each other.

Solve: x 1176  9117

x 1176  1176  9117  1176

x 7941

Check:x 1176  9117

7941 1176 9117 Substitute 7941 for x.

9117  9117 Tr u e

So 7941 is the solution of the addition equation

x 1176 9117.

The Fort McHenry Tunnel is 7941 feet long.

?

Subtract 1176 from both

sides to “undo” the addition

and to isolate x.

Subtraction Property of Equality

addition equation

Key Concept

Subtraction Property of Equality

When you subtract the same

number from both sides of an

equation, you get a true statement.

If ab, then acbc.

addition equation

Think

Whenever you subtract a

number from one side of

an equation, you must

subtract the same number

from the other side to keep

the equation in balance.

The new equation is

equivalent to the original

equation.

Check:x(5)  12

17 (5) 12

12  12 Tr u e

Substitute 17

for x.

?

Equations that have the same solution are called.

x 1176 9117 and x7941 are equivalent equations.

equivalent equations