Question 1066882
Some information is missing.


Imagine you want 100 of whatever weight quantity of the ointment.
x, y, z, the weights of the 3, 15, and 30, of whatever concentration, probably meant as percents.


{{{x+y+z=100}}}-----assuming 100 of your weight units of the mixture


{{{(3x+15y+30z)/100=10}}}-----to account for the resulting 10% concentration mixture


You still need one more described relationship.