Question

Which equation has a slope m=−3/8

Answer 1

I think this is the answer
$y = -\frac{3}{8} x$

hope this helps

Answer 2

General nomenclature of linear equations is

y=mx+b where m is the gradient (or slope) while b is  the y-intercept.

Depending on the value given, b can cross the y axis at any point.

Say
y=-3/8x  .... meaning b=0
y=-3/8x+1 .... meaning b=1

and so forth. So, it depends on the values given or rather the cordinates given.