Answer:
(C) 18
Step-by-step explanation:
We can create a systems of equations. Assuming [tex]m[/tex] is Michelle's age, [tex]j[/tex] is Joan's age, and [tex]r[/tex] is Ryan's age, the equations are:
[tex]m = j + 7[/tex]
[tex]j = r-3[/tex]
[tex]m+j+r = 64[/tex]
We can use substitution, since we know the "values" of m and j.
[tex](j+7)+(r-3)+r = 64\\(j+7)+(2r-3)=64\\2r + j + 4 = 64\\2r + j = 60\\\\[/tex]
[tex]r = 21, j = 18[/tex]
So we know that Joan is 18 years old.
Hope this helped!
