Question 1151808

The total age of three sisters is 79. The youngest is 7 years younger than the middle. The age of the older is twice that of the youngest. What is the age of the middle?
<pre>Let middle sister's age be M
Then the youngest's is: M - 7, and the oldest's is: 2(M - 7) = 2M - 14
The following SUM of AGES equation is formed: M + M - 7 + 2M - 14 = 79
Solve that for M, the middle sister's age.