If TD = SG and MD = SL, then angle D would have to equal angle S in order to prove the triangles congruent by SAS.
(Idk if you had a typo, so I'll solve for the other one, too) If TD = SG and MD = GL then angle D would have to equal angle G in order to prove the triangles congruent by SAS.
The price of the chair afterwards was $176.40. You take $210 and multiply it by .40 and get $84. Then you subtract it from 210 and get 126. Then take 126 multiply it by .40 and get $50.40 then you add it back to the $126 and get $176.40