Cross multiplication will help with this! Since someone with 104 pounds is given a specific amount of medicine but another person with unknown pounds but known medicine is given, cross multiplication is helpful.
We can make it into a fraction, say pounds/milligrams
104 lbs/130mg=x (because it is unknown) lb/278.75
Then we can multiply it by crossing both sides.
130x=104(278.75)
130x=28990 Isolate x by dividing by 130
x=223
The person is 223 pounds who needs 278.75 mg of medicine.
