Question 1204684
<pre>
Mary’s age is 3 more than twice her brother’s age.  The sum of their ages is 33.  What is Mary’s age?

Let Mary's and her brother's ages be M and B, respectively
   Then we get: M = 2B + 3 ---- eq (i)
      Also, M + B = 33____B = 33 - M ----- eq (ii)
                M = 2(33 - M) + 3 ----- Substituting 33 - M for B in eq (i)
                M = 66 - 2M + 3
           M + 2M = 66 + 3
               3M = 69
Mary's age, or {{{highlight_green(matrix(1,5, M, "=", 69/3, "=", highlight(23)))}}}</pre>