You can use these:
A ≥ 5000
C ≥ 195
D ≥ 700
x = 3000A + 45C + 75D
y = 1000A + 50C + 200D
However, the direct combination of these equations/inequalities won't give you the answer that you want.
The number of type x pills necessary:
For vitamin A, you would need to take at least 2 type x pills (5000÷3000 = 1.67 --> 2 pills)
For vitamin C, 195 ÷ 45 = 4.33 ---> 5 pills.
For vitamin D, 700 ÷ 75 = 9.33 ---> 10 pills.
You can make a similar analysis for type y pills.
Then, there is the possibility that you can take a combination of x and y pills.
This can get quite complicated.