3./x-5/=21
=>/x-5/=21:3
=>/x-5/=7
=>x-5=7 hoặc x-5=-7
=>x=12 hoặc -2
kết quả =10 bạn ạ. MÌnh đảm baỏ 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%