Logical task. On a table 3 rulers lay. Yellow, green, blue. The yellow ruler was longer green on 2 cm. Blue is shorter green on 3 cm. Find length of a yellow ruler if length of blue 15 cm.

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1) 15+3 = 18 cm - length of a green ruler. 2) 18+2 = 20 cm - length of a yellow ruler. A blue ruler - 15 cm a green line of-18 cm a yellow line-20 of cm
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