a)
x:10+300=400
x:10=400-300
x:10=100
x=100×10
x=1000
b)
(35+x)×10-25=325
(35+x)×10=325+25
(35+x)×10=350
35+x=350:10
35+x=35
x=35-35
x0
c)
(x-25):5+90=100
(x-25):5=100-90
(x-25):5=10
x-25=10×5
x-25=50
x=50-25
x=25
d)
(200-x):10+90=100
(200-x):10=100-90
(200-x):10=10
200-x=10×10
200-x=100
x=200-100
x=100
e)
500:x+(300:10-20)=60
500:x+10=60
500:x=60-10
500:x=50
x=500:50
x=10
f)
(30×10)-(4×x+50×2)=100
300-(4x+100)=100
4x+100=300-100
4x+100=200
4x=200-100
4x=100
x=100:4
x=25
Succes! =]
