y and x are directly proportional, as stated by hypothesis. Let's use the rule of three to find y when x = 8.
x=5 --> y=12
x=8 --> y=?
? = (8*12)/5 = 96/5 = 19.2
So y directly varies with x, and y=12 when x = 5, then y=19.2 when x=8.
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