What coefficients must be added to balance the following reaction __sn+=h2+(po4)4

Answer 3Sn+ 4H3pO4= 6H2+Sn(PO)4

1 Sn                                  3 Sn
3 H                                    2 H
1 P                                    4 P
4 O                                    16 O
 then you have to make the numbers the same for each side

so you get by putting the 3 infront of Sn 4 infront of the H3PO4  and 6 infront of the H2
3 Sn                                   3 Sn
12 H                                    12 H
4 P                                      4 P
16 O                                     16 O

It's called the falling actionwrong subject by the way

The answer is the third option extremely gradual