write an equation for a line passing through 47 and parallel

write an equation for a line passing through (4,-7) and parallel to line whose equation is: 3x=9-y

Given line is 3x=9-y

i.e.,y=-3x+9

the equation of line parallel to above line is of the form

y=-3x+b

Plug x=5,y=-7 in y=-3x+b

we get -7=-3(4)+b

b=-7+12=5

therefore the required line is y=-3x+5