Pre-Algebra Demystified

ANSWERS

1. x, xþ 5


2. x, 50
   x


3. x, 5x


4. x,^12 xorx,2x


5. x, 2xþ 10

Word Problems

Equations can be used to solve word problems in algebra.
After reading the problem:

 Step 1 Represent one of the unknown quantities as x and the other

unknown by an algebraic expression in terms of x.

 Step 2 Write an equation using the unknown quantities.

 Step 3 Solve the equation for x and then find the other unknown.

 Step 4 Check the answers.

EXAMPLE

One number is 8 more than another number. The sum of the two numbers is

114. Find the numbers.

SOLUTION

Step 1 Let x¼the smaller number
Let x+8¼the larger number
Step 2 x+x+8¼ 114
Step 3 x+x+8¼ 114

2xþ 8 ¼ 114

2xþ 8 
 8 ¼ 114 
 8

2x¼ 106

2 x

2

¼

106

2

x¼ 53

xþ 8 ¼ 53 þ 8 ¼ 61

Hence, one number is 53 and the other number is 61.

Step 4 Check: 53þ 61 ¼114.

CHAPTER 7 Expression and Equations 145