Find the value of a if y=((2a+1)/3)x+b is parallel to y = -x -3

I'm kind of confused of how I should solve this :/ It tells me to find 'a,' but i'm not too sure where to start. Thank you for your help :)

2 answers

Both equations are written in the form y = mx + b
In that form the slope is m

parallel lines have the same slope

for your first, the slope = (2a+1)/3
for the 2nd, the slope = -1

so ....
(2a+1)/3 = -1

solve for a, and you got it.
hollllllyy, thanks.