a: =>(7x-15)x8=48
=>7x-15=6
=>7x=21
hay x=3
\(\left(7x-15\right)8=27+21\\ \left(7x-15\right)8=48\\ 7x-15=48:8\\ 7x-15=6\\ 7x=6+15\\ 7x=21\\ x=21:7\\ x=3\)
\(\left(7x-15\right).8-21=27\\ \Rightarrow\left(7x-15\right).8=48\\ \Rightarrow7x-15=6\\ \Rightarrow7x=21\\ \Rightarrow x=3\)
(7x−15).8−21=27
⇒(7x−15).8=48
⇒7x−15=6
⇒7x=21
⇒x=3