The EPa detection limit for phosphate in water samples is 0.0450 milligrams per liter. Can phosphate be detected if 55.0 nanograms are found in 500.0 mL of solution? Show your calculations and explain.

Convert nanograms to milligrams, and ml to liter

55nanograms/500ml (1000ml/L)(1gram/E9 nanograms)(1000mg/gram)

wont that do it?
YOu can check yourself by typing into the google search window:
55nanograms/500 milliliters in mg/l