97.15 is the area. All I did is multiply both numbers.
When competing the square, you want to have

at the end, and using the fact that the x term and coefficient are really

, we see that the third option is the most efficient way to start
It is 18.02. First you multiply 5.4 by 6.8 because it is a triangle you have to divide it by 2. 5.4x6.8=36.04 36.04/2=18.02
4^3 ab^2
Four would be cubed (to the third power) and ab would be squared (to the second power)