Please help me I will give brainliest

Answer:
60 milligrams
Step-by-step explanation:
just cross multiply! percentages are just fractions of 100. so you can say that [tex]\frac{45}{x} =\frac{75}{100}[/tex]
multiple 75 by x and 45 by 100 and you get
4500=75x
divide both sides by 75 and you get 60