The sum of fifteen and six times a number t is 81

Well the sum is 15+6=21. then you must do 81-21=60. So your answer must be t=60.

We need to turn this phrase into an algebraic equation and then solve...

in math
"of" means times (x)
"is" means equals (=)
"sum" means you're going to add

The sum (we are going to add) of 15 and six times a number t (15 + 6t) is 81 (= 81).  So write it out...

15 + 6t = 81

Now solve for t.  First subtract 15 from each side...

15 + 6t - 15 = 81 - 15
6t = 66

Now divide each side by 6 to get t by itself...

6t/6 = 66/6

t = 11

Done!