Answer:
a0=1
a1=6
a2=2
a3=3
Explanation:
We have to start with the <u>reaction</u>:

We have to start with "
". If we want to balance <u>Cr</u> we have to obtain <u>2 on both sides</u>. Therefore we have to add a "2" on the right side, so:

Then we can balance "
" as a whole. We have <u>6 on the right</u>, we have to have the same amount on the left side, so:

Then we can balance "
". We have 6 on the left, so we have to have the same amount on the right if we already have 2 we have to put a · in front (on the right side) to obtain in <u>total 6</u>, so:

Finally, when we add this last number the
we will have 3 on both sides. Therefore the reaction is <u>already balanced</u>.