What value of f makes the equation 5f+25=450 true?

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Achemist has 200 ml of a 10% sucrose solution. she adds x ml of a 40% sucrose solution. the percent concentration, y, of the final mixture is given by the rational function: the chemist needs the concentration of the final mixture to be 30%. how many milliliters of the 40% solution should she add to the 10% solution to get this concentration?

45% of the trees in a park are apple trees. there are 27 apple trees in the park. how many trees are in the park in all?