What is 20.9/9.31? no need to explain. just need the answer

Which sum or difference identity would you use to verify that cos (180° - ∅) = -cos ∅? a. sin (α -β) = sin α cos β – cos α sin β b. cos (α -β) = cos α cos β – sin α sin β c. cos (α -β) = cos α cos β + sin α sin β d. sin (α + β) = sin α cos β + cos α sin β

Can someone me do math because i am having a breakdown rn because i don’t get it

Acoin bank containing only dimes and quarters has 12 more dimes than quarters. the total value of the coins is $11. how many quarters and dimes are in the coin bank?