Description: Sal uses place value and decomposing numbers to subtract decimals, such as 65.79 - 42.58. For example, if I have 0.69, or 69/100, and from that I want to subtract 0.34, or 34/100, what is that going to be? Well nine ones minus, or I should say nine minus four is gonna be five. Now another way I could think about it is I could break up the tenths, and then the leftover hundredths.*Teacher Advisor is 100% free.