Chapter 8.3, Problem 28STP

To determine

How much did you spend for lunch?

Answer to Problem 28STP

You spend for lunch is $x=6$

Option A is correct

Explanation of Solution

Given:

You and your friend spent a total of $15 for lunch. Your friend’s lunch cost $3 more than yours did

Concept Used:

Rules of Addition/ Subtraction:

• Two numbers with similar sign always get added and the resulting number will carry the similar sign.
• Two numbers with opposite signs always get subtracted and the resulting number will carry the sign of larger number.

Rules of Multiplication/ Division:

• The product/quotient of two similar sign numbers is always positive.
• The product/quotient of two numbers with opposite signs is always negative.

In order to find an equation

Let x be the amount you spent for lunch and $x+3$ for your friend’s cost for lunch

The equation as shown below,

  $x+x+3=15$

Thus, the equation is $x+x+3=15$

In order to solve the equation $x+x+3=15$ , first add the like terms and then subtract both sides by $3$ and then divide both sides by $2$ and then simplify as below:

  $\begin{array}{c}x+x+3=15\\ 2x+3=15\\ 2x+3-3=15-3\\ 2x=12\\ \frac{2x}{2}=\frac{12}{2}\\ x=6\end{array}$

Thus, you spend for lunch is $x=6$

Option A is correct