math
posted by Nina on .
I'm not sure of how to solve word problems. The question is,"One lawn fertilizer is 24% nitrogen and another is 12% nitrogen. How much of fertilizer should be mixed to obtain 100 kg of fertilizer that is 21% nitrogen?"

Nitrogen total=sum of parts
100*.21=.24*x + .12y
but x+y=100
21=.24x+.12(100x)
solve for x first.