Question

A bag contains purple marbles and green marbles, 71 in total. The number of purple

marbles is 9 less than 4 times the number of green marbles. How many purple
marbles are there?

Answer 1

`55 \: purple \: marbles`

Explanation:

`Let \: x, y \: be \: the \: number \: of \: purple \: and \: green \: marbles \: respectively \\ We \: have \: a \: system \: of \: equation: \\ \begin{cases}x + y = 71 \\ x + 9 = 4y \end{cases}\Leftrightarrow \begin{cases}x = 55\\ y = 16 \end{cases}`