Solve for a. 13(21−3a)=6−a all real numbers 0 no solution −1

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

Due to financial difficulties the owner of 4 skateboard stores is going to close 2 of his stores. based on the money earned at each store, which two stores should remain open?

Ab and bc are tangent to circle d. find x is ab = 3x + 8 and bc = 26. find x