a, Ta có: 770:[ ( 20x+10 ):x ] = 35
=>(20x+10):x =770:35
=>(20x+10):x =22
=>20x+10=22x
=>20x+10=20x .2x
=>10=2x
=>x=10:2
=.x=5
b,Ta có: 5x+15-2x=65
=>5x-2x+15=65
=>3x+15=65
=>3x=50
x=50/3
Chúc bạn làm bài tốt
b, 5x+15-2x=65
=>5x-2x+15=65
=>3x+15=65
=>3x=50
=>x=50/3