Answer: 12
Step-by-step explanation:
For AP d=u₂-u₁
therefor taking u₁= 5x+4
u₂= 4x-5
u₃ = 2x-2
u₂-u₁ = u₃-u₂
4x-5 -(5x+4) = 2x-2-(4x-5)
grouping like terms all Xs to the LHS and all numbers on the RHS
4x-5x-2x+4x = -2+5+5+4
By using a calculator, you get
X=12