In-class Exercise

Name ______________

  1. I'm a mystery number. If you multiply me by 3 and then add 4 the result is the same number if you multiply me by 4 and then add 3. What number am I?
    Use X for your mystery number.
    1. The left side of the equation is "multiply me by 3 and then add 4".
        Using X this is _________________
    2. the right side of the equation is "multiply me by 4 and then add 3".
        Using X, this is _________________
    3. Set these two expressions equal to each other and solve.
        ________________________

        X = ____

  2. Trina, who is 10, wants to know how old her mother is. Her mother says two times the difference between our ages is the same as the sum of our ages plus 14 more. How old is her mom?
    Use T for Trina and M for Mom.
    1. Write the expression for "2 times the difference in our ages" =
        ______________
    2. Write the expression for "the sum of our ages +14" =
        ______________
    3. Set these two expressions equal to each other and solve =

        ___________________


        M = _____

  3. On January 1st, Danny has $5 and Alyssa has $131. Each month Danny saves $12 more than he spends while Alyssa spends $6 more than she saves. At the beginning of what month do they have an equal amount of money?
    Use M for the number of months past January.
    1. Write the expression for "$5 plus 12 times the number of months" =
    ___________________
    2. Write the expression for $131 minus $6 times the number of months past January", =
    ___________________
    3. Set these 2 expressions equal to each other and solve:
        __________________________

        M = ___ and that month is ________________
  4. I'm thinking of a number. 8 times my number is the same as 3 times my number plus 65. What is my number?
    Use N for my number.
    1. Write the expression for "8 times my number" =
        ________________
    2. Write the expression for "3 times my number plus 65" =
        ________________
    3. Set these 2 expressions equal to each other and solve:

        ______________________________
        N = ____________