Question

What is the function rule of (1,30) (2,35) (3,40) (4,45)?

Answer 1

$\bf \begin{array}{ccll} x&y\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 1&30\\ 2&35\\ 3&40\\ 4&45\\ a&5(a)+25 \end{array}\qquad \qquad y=5x+25$

if you have already covered slopes, you could also get it that way, in fact is  simpler that way.