Hey there!
Zn + HCl → ZnCl₂ + H₂
First, balance Cl.
1 on the left, 2 on the right. Add a coefficient of 2 in front of HCl.
Zn + 2HCl → ZnCl₂ + H₂
Next, balance H.
2 on the left, 2 on the right. Already balanced.
Lastly, balance Zn.
1 on the left, 1 on the right. Already balanced.
Our final balanced equation:
Zn + 2HCl → ZnCl₂ + H₂
Hope this helps!