You have the following expression:
64 ÷ 42·16
In order to simplify the previous expression, first multiply the factors 42 and 16:
42·16 = 672
next, simplify the fraction 64/672:
64/672 divide by 2 both numerator and denominator
32/336 divide by 2
16/168 divide by 2
8/84 divide by 2
4/42 divide by 2
2/21
Hence, the simplied expression is 2/21