November 5, 2021 CE

Simplifying Linear Equations

Simplify: \( 6x + 3 = x + 8 \)

\begin{align} 6x + 3 &= x + 8 &&\text{Given. Subtract \( 3 \) from both sides.} \tag 1 \\[2ex] 6x &= x + 5 &&\text{Subtract \( 1x \) from both sides.} \tag 2 \\[2ex] 5x &= 5 &&\text{Divide both sides by \( 5 \).} \tag 3 \\[2ex] x &= 1 &&\text{Solution.} \tag 4 \\[2ex] \end{align}

Simplifying Equations Containing Fractions

Simplify: \( \dfrac{3p}{8} + \dfrac{7p}{16} - \dfrac{3}{4} = \dfrac{1}{4} + \dfrac{p}{16} + \dfrac{1}{2} \)

  1. You can greatly simplify this problem by getting rid of all denominators. Try multiplying all terms by their Least Common Denominator (LCD).
  2. Combine the like terms.
  3. Isolate the variable.
\begin{align} \dfrac{3p}{8} + \dfrac{7p}{16} - \dfrac{3}{4} &= \dfrac{1}{4} + \dfrac{p}{16} + \dfrac{1}{2} &&\text{Multiply all terms by 16.} \tag 1 \\[2ex] {\color{red}9p} - {\color{green}12} &= {\color{green}12} + {\color{red}p} &&\text{Subtract 1p from both sides.} \tag 2 \\[2ex] {\color{red}8p} - {\color{green}12} &= {\color{green}12} &&\text{Add 12 to both sides.} \tag 3 \\[2ex] {\color{red}8p} &= {\color{green}24} &&\text{Divide both sides by 8.} \tag 4 \\[2ex] p &= 3 &&\text{Solution.} \tag 5 \\[2ex] \end{align}

Solving Word Problems with One Variable

A phone company charges \$0.027 per minute and a \$2 monthly fee. Another phone company charges \$0.035 per minute with no monthly fee.

  1. Find the number of minutes at which the charges for both companies are the same.
  2. What is that cost?
  1. Let \( m \) = number of minutes
  2. Company A: \( 2 + 0.027m \)
  3. Company B: \( 0.035m \)
  4. Set the expressions equal to each other and solve for $m$: \( 2 + 0.027m = 0.035m \)
Find the number of minutes.
  1. Let \( m \) = number of minutes
  2. Company A: \( 2 + 0.027m \)
  3. Company B: \( 0.035m \)
  4. Set the expressions equal to each other and solve for $m$.

\begin{align} 2 + 0.027m &= 0.035m &&\text{Given. Multiply all terms by 16.} \tag 1 \\[2ex] 2 &= 0.008m &&\text{Divide both sides by 0.008.} \tag 2 \\[2ex] 250 &= m &&\text{Solution.} \tag 3 \\[2ex] \end{align}

Find the monthly charge at which both companies have the same fee.
  1. Let $c$ = the cost at which the charges from both companies are the same.
  2. Multiply the Number of Minutes (250) by the Unit Rate for Company B ($0.035).

\begin{align} c &= 250(0.035) &&\text{Given. Multiply the left side.} \tag 1 \\[2ex] c &= $8.75 &&\text{Solution.} \tag 2 \\[2ex] \end{align}

Solutions
  1. 250 minutes
  2. $8.75 per month