Question

please tell me what to do​

Answer 1

displacement reaction

Answer 2

see guys

MgO which means "magnesium oxide"

H2O we all knows that means "water"

so when the water and magnesium oxide reacts with each other there is a exothermic reaction in which the large amount of heat is produced. and it makes the magnesium hydroxide.

so the Mg(OH)2 is called magnesium hydroxide

and the number 2 is due to balancing of the equation, and in Mg(OH)2 2 is outside the brackets because it multiplies with both O as well as H.