1. vận tốc riêng của canô là t(km/h) lúc nước yên lặng , vận tốc nước chảy là 5(km/h). biểu thức nào là vận tốc lúc ngược dòng của canô. A. b. c. d. 2. gọi x(km/h) là vận tốc của cano thứ nhất . cano thứ hai có vận tốc nhanh hơn cano thứ nhất là 4(km/h). khi đó vạn tốc của cano thứ hai được biểu thị là (dơn vị km/h) A.x-4 B.x*4 C.x+4 D.x/4 3. cho một số có hai chữ số , biết rằng chu8wx số hàng chục gấp ba lần hàng đơn vị. nếu gọi chữ số hàng đơn vị là a(0<a<=9) thì chữ số hàng chục là A.3a B.a+3 C.a-3 D.a/3

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