17 points! what does x = “1/3 x + 8 = 2/3x + 6 solve by susbtitution

Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)

If 25% of y is 30, what is 60% of y?

Need so much on this one how many yards?