Answer:
12
Step-by-step explanation:
The proportion is equal to 
We can simplify the right side by dividing by 7/7 to get the right side equal to 6/5. Now we can cross-multiply to get

Dividing both sides by 5, we have the answer as

By pythagorus theorum In triangle ADC
AD²=AB²-BD²
AD²=(6.2)²-(2.7)²
AD=5.5
Again in triangle ADC
AC²=AD²+BC²
AC²=(5.5)²-(2.5)²
AC²=30.25-6.25
AC=4.8 approx..
That should be 125i. If you have a graphing calculator you should be able to just enter it into the calculator to solve lol