11.73 plus half a 20% tip...so a 10% tip?
There are 2 ways you can do this, you can find the 20% tip, then divide it in half.
11.73 · 0.20 = 2.346
2.346 is you 20% tip, you divide it in half which equals 1.173
11.73 + 1.173 = 12.903
Another way is just finding the 10% tip
11.73 · 0.10 = 1.173
11.73 + 1.173 = 12.903
or you could do:
11.73 · 1.10 = 12.903
You can do whichever way you learned it. Your answer is 12.903, if you round it, it will be 12.90