Fractions of fractions

If you know that a fraction of X is the same as a different fraction of Y, can you work out X/Y?
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Problem



Two thirds of five sixths of a number $X$ is the same as three quarters of four fifths of a number $Y$.

What is the value of $\frac{X}{Y}$ as a fraction in its lowest terms?

 

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.