?% of 280 + 18% of 550 = 143.8 (a) 11 (b) 18 (c) 21 (d) 16 (e) None of these
280*x/100+550*18/100=143.8280*x/100+99=143.8280*x/100=143.8-99280*x/100=44.8=44.8*100/280=16% answer