Here you have black dots at x = {0, 1, 2, 4, 4.5, 5}.
For each of these x-values, there is one and only one associated y-value. This fact tells us that the graph does represent a function.

= 7.348469228
this is irrational, because it cannot be written in the form

2. Irrational
Set up a proportion: 3/10= x/80. Then if you multiply 10 by 8, you get 80 on both sides, But, If you do it to the top, you also have to do it to the bottom, so the anser is 3 x 8 , or 24.