Variable as Placeholder Math Example 5

Follow the full solution, then compare it with the other examples linked below.

Example 5

medium
I think of a number, double it, and add 5 to get 19. What is my number?

Solution

  1. 1
    Let xx be the unknown number: 2x+5=192x + 5 = 19.
  2. 2
    Solve: 2x=142x = 14, so x=7x = 7.

Answer

x=7x = 7
The variable is a placeholder for the specific number you are thinking of. The equation models the described operations.

About Variable as Placeholder

A variable acts as a placeholder — a letter or symbol (like x, n, or y) that stands in for an unknown or changing number in a mathematical expression or equation. It represents one specific unknown value that satisfies a given condition.

Learn more about Variable as Placeholder →

More Variable as Placeholder Examples

Example 1 easy

In the equation [formula], what specific value does [formula] represent?

Example 2 medium

A rectangle has area 24 cm² and width 4 cm. Use a variable to find the length.

Example 3 medium

Maria has some stickers. After giving away 8, she has 15 left. Write an equation and find how many s

Example 4 easy

Find the value of [formula] in [formula].

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