To solve each of these proportions for the missing variable, we can use the property that the cross products of a proportion are equal.

1) -3/5 = 4/x
Cross multiply: -3x = 20
Divide by -3: x = -20/3 or approximately -6.67

2) -1/9 = 3/x
Cross multiply: -x = 45
x = -45

3) 4/1 = 20/x
Cross multiply: 4x = 20
x = 5

Therefore, the solutions for the missing variables are:
1) x = -20/3 or approximately -6.67
2) x = -45
3) x = 5