The red rope was four times the length of the blue rope. The blue rope was 7 centimeters shorter than the yellow rope. If the 3 ropes had a combined length of 37 centimeters, what was the length of the red rope in centimeters?
Let Y = the length of the yellow rope in centimeters.
Blue rope = Y - 7.
Red rope = 4 * (Y - 7)
Y + Y - 7 + 4 (Y - 7) = 37 cm
6Y - 35 = 37
6Y = 72.
Y = 
<gadget id="calculator">12</gadget>
<output>12</output>
12 cm.
The red rope was 20 cm long.

<result>20</result>