Joel = j, Mark = m, Sandra = s
j + m + s = 120
m = 3j
j = 1/2 s --> s = 2j
plug in (substitute) each letter to make it in terms of only j: j + m + s = 120
j + 3j + 2j = 120
6j = 120
6j/6 = 120/6
j = 20
now plug in for the j & s equation:
s = 2j = 2(20) = 40
Therefore Sandra has 40 coins!
Answer:
acceleration 
Step-by-step explanation:
The acceleration is the change in velocity per unit of time.
Therefore to have this rate in appropriate units that can combine, we re-write the change from 0 to 70 km/h in meters per second using:

so in this case the acceleration becomes:

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Answer:
Not a function because it does not pass the Vertical Line Test.