Question

???

r + 3r + _ = 6r

3
2
3r
2r

Answer 1

2r because adding 3r and r gets you 4r so you would need 2 more

Answer 2

2r

Explanation:

r+3r+_=6r

4r+_=6r

Subtract 4r from both sides.

_=2r

Therefore the answer is 2r.