Convert the grams into milligrams. 0.5 = 500 (to covert you'll multiply .5 x 1000).
D/H x Q will be the formula to use now that we have like terms (mg).
D= dose to give
H = dose that is supplied
Q= quantity to give
In this case your numbers will be
D = 500mg
H = 250mg
Q = 1 tablet
500 ÷ 250 = 2
2 x 1 = 2
So, that means you will give 2 tablets to your patient.