Câu hỏi 21
Các số nguyên $0\leq a,b,c,d\leq9$ thỏa mãn
$$\begin{gathered}6a+9b+3c+d=88\\a-b+c-d=-6\\a-9b+3c-d=-46.\end{gathered}$$
Tính $1000a+100b+10c+d$.
$$\begin{gathered}6a+9b+3c+d=88\\a-b+c-d=-6\\a-9b+3c-d=-46.\end{gathered}$$
Tính $1000a+100b+10c+d$.