Determine if the following ratios form proportions. 1.) 1 to 3 and 7 to 21

2.) 3 to 4 and 24 to 18

3.)1:5 and 6:30

for brainiest:)

1. Proportional

2. Not proportional

3. Proportional

Step-by-step explanation:

We have three questions with 2 ratios and are asked if they are proportional or not.

To define proportionality, basically its if the two ratios equal the same value when put in a certain way.

And that way is :

You will substitute the numbers with the letters, in which you will cross multiply :

So subtitute :

1.

Therefore 1. is proportional.

2.

96 = 54

Therefore 2. is not proportional.

3.

30 = 30

Therefore 3. is proportional.

= 5

step-by-step explanation:

to find the 15th term substitute n = 15 into the nth term formula

= (- 3 × 15 ) + 50 = - 45 + 50 = 5