Another Word Problem.

A hospital received a shipment of 8-milligram doses of a medicine. Each 8-milligram package was repacked into two smaller doses of unequal size and labeled packet A and packet B. The hospital then used 17 doses of packet A and 14 doses of packet B in one week. The hospital used a total of 127 milligrams of the medicine during that week. How many milligrams of the medicine are contained in each A packet? In each B packet?

this is all i can think of:
(A-17)+(B-14)=127
+17, +14, -B
A = 158-B

but then if i plugged it back in it would look like this
158 - B - 17 + B -14 = 127
but that doesn't work because the Bs cancel each other out.

I seriously don't understand word problems.