Question

12 1supra2+23 7supra2

Answer 1

12 intregi 1/2 = (12*2+1)/2 = 25/2
23 intregi 7/2 = (23*2+7)/2 = 53/2 
25/2+53/2 = 78/2 = 39

Answer 2

$12\dfrac{1}{2}+23\dfrac{7}{2} = \\ \\ = 12+\dfrac{1}{2}+23+\dfrac{7}{2} = \\ \\ = 35+\dfrac{1}{2}+\dfrac{7}{2} = \\ \\ = 35+\dfrac{1+7}{2} = \\ \\ = 35+\dfrac{8}{2} = \\ \\ = 35+4 = \\ \\ = 39$