?% of 280 + 18% of 550 = 143.8 (a) 11 (b) 18 (c) 21 (d) 16 (e) None of these
x/100*280+18/100*550=143.8=>14x/5+99=143.8=>14x/5=44.8=>14x=224=>x=16hence the answer is 16.