First find the slope between any two points:
[tex]\sf Slope=\frac{y_2-y_1}{x_2-x_1}[/tex]
Where [tex]\sf (x_1,y_1),(x_2,y_2)[/tex] are the two points
So calculating the slope:
[tex]\sf Slope=\frac{7-5}{2-1}=\frac{2}{1}=2[/tex]
So the slope is [tex]\boxed{2}[/tex]
And our equation will be in the format of [tex]\sf y=mx+b[/tex]
where [tex]\sf m~ is~ the ~slope[/tex] and [tex]\sf b ~is~the~y-intercept[/tex]
So, now we have half of the equation:
[tex]\sf y= 2x+b[/tex]
Now to calculate b, we can plug in a point [tex]\sf (x,y)[/tex] and solve for b.
So
[tex]\sf y= 2x+b[/tex]
Lets use the point
[tex]\sf (1,5) which ~is~in~the~form ~of ~(x,y)[/tex]
So:
[tex]\sf 5=2(1)+b[/tex]
And then:
[tex]\sf b=3[/tex]
So our final equation is [tex]\sf \boxed{y=2x+3}[/tex]