<span>64 + 16 = 60 + 10 + 4 + 6 = 70 + 10 = 80
70 - 24 = 70 - 20 - 4 = 50 - 4 = 46
90 - 23 = 90 - 20 - 3 = 70 - 3 = 67
35 + 35 = 30 + 30 + 5 + 5 = 60 + 10 = 70
37 + 43 = 30 + 40 + 7 + 3 = 70 + 10 = 80
90 - 68 = 90 - 60 - 8 = 30 - 8 = 22</span>
1) (607+639)-(439+403)=404.
2) (871+706)-(304+471)=802
Вот как то так ..............