What is the equation of the line that goes through (1,3) and (5,12) ?

Equation of the line y=mx+b    this line  goes through (1,3) and (5,12)
so    3=m*1+b
and 12=m*5+b
solve the system of equations

second equation minus first is:
12-3=5m+b-m-b
9=4m
m=9/4
m=2.25

3=m+b
3=2.25+b
b=0.75

equation of the line y=mx+b
y=2.25x+0.75
  equation of the line  is y=2.25x+0.75

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