Fe + H2SO4 --> Fe2(SO4)3 + H2

I assume you have to balance the reaction?

a Fe + b H₂SO₄   →   c Fe₂(SO₄)₃ + d H₂

Count the number of times an element occurs on either side of the reaction. These numbers must be equal.

Fe: a = 2c

H: 2b = d

S: b = 3c

O: 4b = 12c

Two of these equations depend on c, so we can treat it as a free variable. Let c = 1. Then a = 2 (Fe) and b = 3 (S), from which it follows that d = 6 (H). So the balanced reaction is

2 Fe + 3 H₂SO₄   →   1 Fe₂(SO₄)₃ + 6 H₂

option 3 . (5x + 1) - (-10x + 6)

step-by-step explanation:

option 1 :

(4x + 3) + (-9x + 4)

or 4x+3 -9x + 4

or -5x + 7

option 2

(x - 2) - (6x - 9)

or x-2-6x + 9

or -5x + 7

option 3

(5x+ + 6)

or 5x + 1 + 10x -6

or 15x -5

option 4

-4x+2x+7-3x

-7x + 2x + 7

-5x + 7

hence only option 3 did   not satisfy the given simplify expression.