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Answer:
First Train = 66miles/hour
Second Train=87miles/hour
Step-by-step explanation:
According to the Question,
Let, Speed of The First Train be X .
So, The Speed of the Second Train will be X+21 .
612/4 = X + (X+21)
153 = 2x+21
2x = 132
x=66 Now, Put This Value,We get
Speed of The First Train be X=66miles/hour .
And, The Speed of the Second Train will be X+21 ⇔ 66+21 = 87miles/hour.