解:1元 = 10角1角 = 0.1元5角 = 0.5元2角 = 0.2元设1角的有x枚,则:5角的有30 - x枚0.1x + 0.5 (30 - x )= 8.20.1x + 15 - 0.5x = 8.20.4x = 6.8x = 6.8 ÷ 0.4x = 1730 -x = 30 - 17 = 13所以,1角的有17枚,则:5角的有13枚
设1角的有x枚10x + 50(30-x) =820x = 171角的有17枚,5角的有13枚