First distribute 5r to the 3r and -4 to get 15r^2-20r
Second distribute 2 towards 3r and -4 to get 6r-8
Aftr your whole eqausion should look like
15r^2-20r+6r-8
Since 15r^2 cant be added to anything leave it as is and the rest of the equation should be this
15r^2-14r-8
It should be easy to figure out from there