How much powdered milk and water would you need to make exactly 5 tablespoons of Milk?

Well- there are 16 Tb. in a cup, so you want .3 times the values for a cup; depends on the directions for the product you're using. You should probably just mix up 1/2 cup and measure out 5 Tb. (a bit over 1/4 c.), unless you enjoy arithmetic.