Use one of the services below to sign in to PBS: You've just tried to add this video to My List. But first, we need you to sign in to PBS using one of the services below. You've just tried to add this ...
Key points Word problems that can be solved by the same arithmetic operation have varying difficulty. Problems that involve the inverse relation between addition and subtraction are more challenging.
Some results have been hidden because they may be inaccessible to you
Show inaccessible results
Feedback