The forgetful pupil bought every day a notebook and the handle. After the price of a notebook raised by 15% and the price ruchk 5% that the total cost of 13%. skok costs tetr if the handle cost 9 kopeks.

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Resheniye: Handle cost is known to us - 0.09 rubles, then we will designate the cost of a notebook through - X. On a statement of the problem, originally total cost of the handle and a notebook will be equal to X + 0.09. After increase in cost, the new price will be equal 1.15X + 0.09 x 1.05 = 1.15X + 0.0945. Knowing a condition that the total cost increased by 13 percent, we will work out the equation 1.15X + 0.0945 = 1.13 (X + 0.09). Solving the equation we receive, 1.15X + 0.0945 = 1.13X + 0.1017. 0.02X = 0.0072. from where X = 0.36. Answer: the cost of a notebook is equal 0.36 rubles.
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