8 pens in a bag, 3 blue, 5 red. 2 taken out at random, without replacement. Probability they are the same colour?

Either both blue or both red. 'OR' rule - add probabilities.Blue - first blue and second blue - 'AND' rule - multiply probabilities. 3/8 x 2/7 (as not replaced) = 6/56 = 3/28 (multiply top and bottom)Red - 5/8 x 4/7 = 20/56 = 5/143/28 + 5/14 = 3/28 + 10/28 = 13/28

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Anna has 4 cakes. Three of them are squares with sides of length x, and one is rectangular and measures 2 by (3x+2). The total area of all the cakes is 13. What is the length of x?


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