Jack bought 90 marbles. After giving away some marbles to his 3 friends, he had 15 marbles left. Find the average number of marbles each of hid friends received.

Hi Xin, 
Please find below the solution to the asked query :

$$\begin{gathered} \mathrm{Total} \mathrm{number} \mathrm{of} \mathrm{marbles} \mathrm{with} \mathrm{Jack} = 90 \\ \mathrm{Now}, \mathrm{Jack} \mathrm{gave} \mathrm{some} \mathrm{marbles} \mathrm{to} \mathrm{his} 3 \mathrm{friends}. \\ \mathrm{Number} \mathrm{of} \mathrm{marbles} \mathrm{left} \mathrm{with} \mathrm{Jack} = 15 \\ \mathrm{Number} \mathrm{of} \mathrm{marbles} \mathrm{given} \mathrm{by} \mathrm{Jack} = 90 - 15 = 75 \\ \mathrm{Now}, \mathrm{average} \mathrm{number} \mathrm{of} \mathrm{marbles} \mathrm{received} \mathrm{by} \mathrm{each} \mathrm{friend} = \frac{\mathrm{Number} \mathrm{of} \mathrm{marbles} \mathrm{given} \mathrm{by} \mathrm{Jack} }{3} \\ \mathrm{average} \mathrm{number} \mathrm{of} \mathrm{marbles} \mathrm{received} \mathrm{by} \mathrm{each} \mathrm{friend} = \frac{75}{3} = 25 \end{gathered}$$

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