Ammonium phosphate is used in lawn fertilizer. For each 1000.-gram quantity of (NH4)3PO4 in lawn...?

For per 1000gm of (NH4)3PO4. 281.5gm of Nitrogen is present. See How, first find out the gram molecular m of Ammonium Phosphate i.e. 149gm. You could note that in 149gm of the fertilizer 42gm of Nitrogen is present. So, divide 1000 by 149 and we'll get 6.7. Then multiply 6.7 to 42 to get the required solution.