back to math video class
Example of word problem solving 2
Question:
What number decreased by 12 equals 5 times the number?
Solution:
Let the number be x
The number decreased by 12 expressed as x - 12
5 times the number expressed as 5x
Given: the number decreased by 12 equals 5 times the number
So we get the equation:
x - 12 = 5x
Move all veriables to the left side of the equation and move all numbers to the right side of the equation
x - 5x = 12
- 4x = 12
divide -4 in both side of the equation
x = -3
so x = -3 is the solution
Remark:
when move one term to other side of the equation, the item will change sign.

This problem is translating english words into a mathematics expression and writting an equation. Let the number be x, then the number decreased by 12 can be written as x - 12. Five times the number can be written as 5x. The relationship is that the number decreased by 12 equals 5 times the number. So we get the equation x - 12 = 5x. Now make the equation into the standard form ax = b, then x = b/a. Check the value of x to see if it satisfy the equation.