# Thread: End of a simplification plroblem

1. ## End of a simplification plroblem

Could someone please explain the step directly under "add the constants" at the bottom I'm not understanding how they arrived at the 9/20 fraction thank you

2. ## Re: End of a simplification plroblem

Originally Posted by eetrapnoel
Could someone please explain the step directly under "add the constants" at the bottom I'm not understanding how they arrived at the 9/20 fraction thank you

This is just arithmetic

$- \dfrac{3}{5} + \dfrac{21}{20} = - \dfrac{3}{5} * 1 + \dfrac{21}{20} = \dfrac{-3}{5} * \dfrac{4}{4} + \dfrac{21}{20} = \dfrac{4(-3)}{4 * 5} + \dfrac{21}{20} = \dfrac{-12}{20} + \dfrac{21}{20} =\dfrac{21 - 12}{20} = \dfrac{9}{20}.$