Learn how to use first, then and now stories to understand addition. First, then, now (subtraction) Learn how to use first, then and now stories to understand subtraction problems. Subtraction within ...

To add -4 and 5, draw the starting number on a number line and count to the right when adding numbers. What is the difference in temperature between a desert at 40 °C and a mountain top at -2 °C? \(40 ...