Question

 ko phải bài thi , chi tiết ạ .

Answer 1

\(a,x-105:21=15\\ x-105=315\\ x=420\\ \Rightarrow x=420\\ b,\left(2x-1\right).5^4=3.5^5\\ \left(2x-1\right)=3.5\\ 2x-1=15\\ 2x=16\\ x=8\\ \Rightarrow x=8\\ \)