Answer:
52.5 Seconds
Step-by-step explanation:
Let's call, her time for the third race, x.
To find the average (53.4), we add up all the values and then divide this total by the number of values.
So, we will set up our equation.
56.4 + 51.3 + x
> ------------------------ = 53.4
3
To get rid of 3, we will multiply both sides by 3.
> 56.4 + 51.3 + x = 160.2
> 107.7 + x = 160.2
We will subtract 107.7 from both sides to isolate x.
