Question

715 + ( 215 + 15 ) помогите решить

Answer 1

7/15 + ( 2/15 + 1/5 ) = 4/5
1) 2/15 + 1/5 = 2/15 + 3/15 = 5/15 = 1/3
2) 7/15 + 1/3 (5/15) = 12/15 = 4/5