Step-by-step explanation:
in a proportional relationship, one variable is always a constant value times the other.
and as such, (0, 0) is always a point of that relationship too.
in general that means the equation is
y = ax
with a being the constant.
using the given point :
4 = a×20
a = 4/20 = 1/5
so, the equation is y = x/5
