Sums involving two-digit numbers or multiplication or subtraction were beyond him.

当加法的和是一个两位数或做乘法和减法时，查尔斯便无能为力。

youdao

In subtraction, one never "carries" a digit or bit on to the next left place-weight.

在减法，一个从来没有“携带”数字或比特的下一个离开的地方体重。

youdao

Based on sign digit negabinary representation, the two step addition and one step subtraction of arbitrary length operands can be performed.

基于符号数字负二进制表达，提出了任意字长操作数的并行两步加法与一步减法。

youdao

This is helpful when parents know the specific subject the child is working on, like double-digit subtraction.

WSJ: The Digital Solution: A Review of LeapsterGS