每本练习本3角，买7本练习本需要多少元？9h5C0y8W+s
算式：提示)g9L*d1m'Y(z7d.n9h5C0y8W+s
答：买7本练习本需要.X*G4[*^.T.B'p5_4|*E._9O+W元。9h5C0y8W+s