7元=70角设1角的x个,5角的y个,1元的z个x+5y+10z=70x+y+z=15∴4y+9z=55∴y=(55-9z)/4 (3) 所以z可取值0,1,2,3,4,5,6.此时对应的y为 y1=(55-0)/4=13.75 y2=(55-9)/4=11.5 y3=(55-18)/4=9.25 y4=(55-27)/4=7 y5=(55-36)...