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Lindsay is 5 years younger than Mark. Seven years ago, the sum of their ages was 31.
Let 
l be Lindsay's age and let 
m be Mark's age.
Which system of equations represents this situation?
Choose 1 answer:
(A) 
{[l=m+5],[(l-7)+(m-7)=3]:}
(B) 
{[l-7=(m-7)-5],[l+m=31]:}
(C) 
{[l=m-5],[(l-7)+(m-7)=3]:}
(D) 
{[l-7=(m-7)+5],[l+m=31]:}

Lindsay is 55 years younger than Mark. Seven years ago, the sum of their ages was 3131 .\newlineLet l l be Lindsay's age and let m m be Mark's age.\newlineWhich system of equations represents this situation?\newlineChoose 11 answer:\newline(A) {l=m+5(l7)+(m7)=3 \left\{\begin{array}{l}l=m+5 \\ (l-7)+(m-7)=3\end{array}\right. \newline(B) {l7=(m7)5l+m=31 \left\{\begin{array}{l}l-7=(m-7)-5 \\ l+m=31\end{array}\right. \newline(C) {l=m5(l7)+(m7)=3 \left\{\begin{array}{l}l=m-5 \\ (l-7)+(m-7)=3\end{array}\right. \newline(D) {l7=(m7)+5l+m=31 \left\{\begin{array}{l}l-7=(m-7)+5 \\ l+m=31\end{array}\right.

Full solution

Q. Lindsay is 55 years younger than Mark. Seven years ago, the sum of their ages was 3131 .\newlineLet l l be Lindsay's age and let m m be Mark's age.\newlineWhich system of equations represents this situation?\newlineChoose 11 answer:\newline(A) {l=m+5(l7)+(m7)=3 \left\{\begin{array}{l}l=m+5 \\ (l-7)+(m-7)=3\end{array}\right. \newline(B) {l7=(m7)5l+m=31 \left\{\begin{array}{l}l-7=(m-7)-5 \\ l+m=31\end{array}\right. \newline(C) {l=m5(l7)+(m7)=3 \left\{\begin{array}{l}l=m-5 \\ (l-7)+(m-7)=3\end{array}\right. \newline(D) {l7=(m7)+5l+m=31 \left\{\begin{array}{l}l-7=(m-7)+5 \\ l+m=31\end{array}\right.
  1. Define Variables: Let's define the variables based on the information given:\newlineLet ll be Lindsay's current age.\newlineLet mm be Mark's current age.\newlineWe are told Lindsay is 55 years younger than Mark, which gives us the equation:\newlinel=m5l = m - 5
  2. Represent Ages Seven Years Ago: Next, we need to represent the information about their ages seven years ago. Seven years ago, Lindsay's age would be l7l - 7 and Mark's age would be m7m - 7. The sum of their ages at that time was 3131, so we have the equation:\newline(l7)+(m7)=31(l - 7) + (m - 7) = 31
  3. Simplify Equation: Now, let's simplify the second equation:\newlinel7+m7=31l - 7 + m - 7 = 31\newlinel+m14=31l + m - 14 = 31\newlinel+m=31+14l + m = 31 + 14\newlinel+m=45l + m = 45
  4. Form System of Equations: We have two equations now:\newline11. l=m5l = m - 5\newline22. l+m=45l + m = 45\newlineThis system of equations represents the situation given in the problem. Let's match this system with the answer choices.
  5. Match with Answer Choices: Comparing our system of equations with the answer choices, we find that:\newlineChoice (C) {l=m5,(l7)+(m7)=31}\{l = m - 5, (l - 7) + (m - 7) = 31\} matches our system of equations.

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