A very important aspect to keep in mind here - you don't actually have 4
You're dealing with the sulfate anion,
This means that you can try to balance the equation either by looking at individual elements, like the other answer attempts to do, or by taking the sulfate anion as a group.
The latter options implies that you have 2 hydrogen atoms, 1 sulfate group, and 1 iron atom on the left side of the equation, and 2 iron atoms, 2 hydrogen atoms, and 3 sulfate groups on the right side of the equation.
Balance the sulfate group first and focus on the rest of the species afterwards. So, you have three times more sulfate groups on the right hand side of the equation
By multiplying this compound by 3, you've increased the number of hydrogen atoms on the left hand side to 6
Finally, you've got 2 iron atoms on the right hand side
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