Subtraction level 4

Today I was doing my subtraction 4. The thing that I found hard to do was 64 - 34 but I had found a way to solve the problem by going 60 + 4 = 64 then i went 64 - 10 = 54 then go 54 - 20 = 34 so then I went 34 - 4 = 30 and there I had my answer. The thing that I found easy was 70 - 40 because all I went like was count back from 70 like 70, 60, 50, 40 and then I had my answer.