Câu hỏi 7Cho $x=\frac1{\log_{1/3}(1/2)}+\frac1{\log_{1/5}(1/4)}+\frac1{\log_{1/7}(1/8)}$. Khẳng định nào đúng?$1.5\lt x\lt2$$2\lt x\lt2.5$$2.5\lt x\lt3$$3\lt x\lt3.5$$3.5\lt x\lt4$