Muffins 3

Adela went out and bought some muffins. She gave 27 to Jack and 2/7 of the rest to her brother. She is then left with 1/2 of the number of muffins she had before. How many muffins did Adela have at first?

Correct answer:

n =  90

Step-by-step explanation:

$$\begin{gathered} n-27-\frac{2}{7}\cdot (n-27)=\frac{n}{2} \\ n-27-2/7\cdot (n-27)=n/2 \\ 3n=270 \\ n=\frac{270}{3}=90 \\ n=90 \end{gathered}$$

Try another example