<span>We know that the runner completed her first race in 17.8 seconds and that she completed her second race in 16.9 seconds. Then the difference between the first race and the second race is .9 seconds. Now we divide .9 by 17.8 and multiply by 100 to get the percent decrease. We get 5.06%. The percent decrease in her time is 5%.</span>
Answer:
All the options are correct
All u have do do is add 12 ×56 and u will get 627 so they will wash 56 cars
If 
and 
, then you can replace 
in either equation with the equivalent expression given by the other equation. In this case, you have
and you can solve for 
.
Then 
.
For the second system, you can write
Then substitute this into the second equation and you get
so that
