Answer:

1.  1:3=3:9

2. 4:3=20:15

3. 1:2:3=4:8:12

Step-by-step explanation:

Steps:

let x be the missing term

then cross multiply

1. 1:3=3:x

   1:3

   3:x

3 x 3

X x 1

x=3x3

x=9

2.4:x=20:15

 4:x

20:15

20x=60

divide both sides by 20

x=30

3. 1:2:3=4:__:12

the third one I just thought of a number that would equal the ratio

1:2:3=4:8:12

man Im bad at explaining things