Pre-Algebra Demystified

SOLUTION

1. xþ 15


2. 2x
   7


3. 6x


4. 3(xþ5)


5. x 4

In solving word problems it is also necessary to represent two quantities

using the same variable. For example, if the sum of two numbers is 10, and

one number is x, the other number would be 10
x. The reason is that given

one number, say 7, you can find the other number by subtracting 10
7to

get 3. Another example: suppose you are given two numbers and the condi-

tion that one number is twice as large as the other. How would you represent

the two numbers? The smaller number would be x, and since the second

number is twice as large, it can be represented as 2x.

EXAMPLE

Represent algebraically two numbers such that one number is three more

than twice the other number.

SOLUTION

Let x¼one number

Let 2xþ 3 ¼the other number

EXAMPLE

Represent algebraically two numbers such that the difference between the

two numbers is 7.

SOLUTION

Let x¼one number

Let x
 7 ¼the other number

PRACTICE

1. Represent algebraically two numbers so that one number is 5 more
   than another number.


2. Represent algebraically two numbers so that their sum is 50.


3. Represent algebraically two numbers such that one number is five
   times larger than another number.


4. Represent algebraically two numbers such that one number is half
   another number.


5. Represent algebraically two numbers such that one number is 10 more
   than twice the other number.

144 CHAPTER 7 Expression and Equations