Need help with this question on microeconomics. The answers are already given but I don't understand where they come from. Can you please explain where every comes from and what to do with it?

25. Consider a market where Demand is D = 450 - 10p and Supply is S = 10p - 50. . The equilibrium price is equal to 450 + 50 p* 20 - = 25, q = 200 b. At equilibrium, the own-price elasticity of demand is equal to 250 - 150 200 ) 25 nxx 30 - 20 X ; 10 =1.25 25 At equilibrium, the own-price elasticity of supply is equal to 250 - 150 200 nxx 30 - 20 = 1.25 25 d. At equilibrium, consumer surplus is equal to CS = (45 -25) x 200 = 2000 2 e. At equilibrium, producer surplus is equal to PS = (25 - 5) x 200 2 = 2000