a)
3-(17-x)=289-(36+289)
3-(17-x)=-36
17-x=-33
x=-16
b)
x+3/10=17/12-17/20
x+3/10=17/30
x= 4/15
c)
x/20=7/12+11/30
x/20=107/60
x.3/60=107/60
x.3=107
x=107/3
d)
7/x<x/4<10/x
<=> 7 < x^2/4 < 10
<=> 28 < x^2 < 40
x nguyên dương => x^2 = 36
=> x=6
Hơi khó nhìn thông cảm nha ! =)))