The negative numbers are smaller than the positive ones. The larger number behind the negative sign is smaller. Therefore, -8.91 is smaller than -2.8 so -8.91 is first and -2.8 is second. The last two numbers are positive so you compare them. 0.62 is smaller than 4.56 so the list of decimals from smallest to largest is -8.91, -2.8, 0.62, 4.56.
