Answer:
equation: y = 3x + 9
Explanation:
first take two coordinates: ( 1 , 12 ) , ( 2 , 15 )
find slope:

:

: 3 ...........this is our slope, m
use the formula to solve or equation: y - y1 = m( x - x1 )
y - 12 = 3 ( x - 1 )
y = 3x - 3 + 12
y = 3x + 9