Help me figure out if these math problems are "linear"

We are talking about linear graphs at school. I don't understand linear.it shows a able and asks if it is linear.
the first problem is:
Number of Costumes: 2 4 6 8
Fabric(yd)7 14 21 28

and the next one is:
Day 1 2 3 4
Distance 21.8 43.6 68.8 90.6

I am pretty sure the first one is linear, but I dont know about the second one because where is says " distance" it is not going up the same ammount each time.

I just need simple help. Im in pre-algebra. Just a simple explanation, we arent dealing with exponets next to the numbers and all that.

thanks in advance! :)

Hello,

Simple criterion:
Divide the array second line terms by their respective first line term.
If this ratio is constant thorough the whole array, then the relation is linear.

In your case:
7 yards of fabric ↔ 2 costumes    thus 7/2 yard/costume
14 ↔ 4    thus 14/4 = 7/2
21 ↔ 6    thus 21/6 = 7/2
28 ↔ 8    thus 28/8 = 7/2
Thus the relation is linear.

On the other hand:
21.8 distance ↔ 1 day    thus 21.8
43.6 ↔ 2    thus 21.8
68.8 ↔ 3    thus 22.93
No need to check further, only one change means the relation is NOT linear.

If you don't understand the concept of linearity.