Answer:
eqn of line : x-3y=15
slope1=m= -coefficient of x/coefficient of y=1/3
As lines are parallel slope must be equal.
slope3=m'=1/3
passing points of second line =(0,7)
eqn of line = (y-y')=m(x-x')
=(y-7)=1/3(x-0)
=y-7=1/3x
=1/3x-y+7=0
=x-3y+21=0
Explanation: