5. Brown has his own bakery. He baked 5 cakes per day. Due to the occasion of Christmas, he started to bake 12 cakes per day. In the whole Christmas week how many cakes will he bake? and the constant is 12
If Brown baked 5 cakes per day, and now he bakes 12 cakes per day, he is baking an additional 12-5= <<12-5=7>>7 cakes per day.
Thus, in the whole Christmas week which lasts for 7 days, he will bake an additional 7*7=49 cakes.
So in the Christmas week, he will bake a total of 7*12 + 49= <<7*12+49=125>>125 cakes. Answer: \boxed{125}.