book Maths Puzzle Numerical Ability

Two trains leave Chicago, one traveling East at 30 miles per hour, and one traveling west at 40 miles per hour. When will the trains be 210 miles apart?
(We are supposed to be using the formula d=rt.)

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If x = �1 and y = 2, what is the value of the expression 2x3 � 3xy ? question 1000=20(1/0.015 - 1/0.015(1.016)t(power of t)
my progress
1000 = 1333.33 - 66.67/(1.06)t
66.67/(1.016)t= 1333.33-1000

66.67= 333.33(1.016)t

0.2 =(1.016)t where d