Question

clear parentheis and comebine 2 (s+6)-(8s-t)+6t

Answer 1

First multiply out the brackets
2(s+6) = 2s+12
-(8s-t) = -8s+t (Don't forget to distribute the - so that t becomes -t)
+6t
Bringing it all together:

2(s+6)-(8s-t) +6t =
2s+12- 8s+t +6t

Grouping like terms (combine s terms together, likewise t terms, likewise the number term) gives:

-6s+7t+12