Question

Số?

a) 7 + 4 = 7 + .?. + 1

    7 + 7 = 7 + .?. + 4

b) 6 + 5 = 6 + .?. + 1

    6 + 6 = 6 + .?. + 2  

Answer 1

a) 7 + 4 = 7 + 3 + 1

   7 + 7 = 7 + 3 + 4

b) 6 + 5 = 6 + 4 + 1

   6 + 6 = 6 + 4 + 2