Answer:

Step-by-step explanation:
sine of A = 
opposite = 5
adjacent = 12
hypotenuse = 13
You start by figuring out how fast a lap is so you do
4.5 (4 1/2 miles)/3
=1.5 minutes
Which means it takes her 1.5 minutes to do 1/4 mile so you times that by four to get how long it takes her to run a mile
4x1.5
=6
This means it takes her 6 minutes to run a mile
To get this into miles per hour you divide 60 (because there’s 60 minutes in an hour) by 6 (her mile time)
60/6
=10
Therefore she is running 10 miles per hour
We can solve it algebraically:

(subtract 4 from both sides to isolate


(square both sides to get rid of square root on left side

(divide both sides by 3 to isolate y)
Answer:
she started with 50 marbles
Step-by-step explanation:
The total is 100 than you just subtract 20 and 30 becasue that is what is added later on. After you subtract 20 and 30 from 100 you will get 50. Therefore Sara had started out with 50 marbles.
Hope that helps :)