Summing Fractions

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I realize that this is basic arithmetic, but I really can't see how these terms combine...

here goes:

$4[(.5)^4\cdot (.6)^3]+4[(.5)^4\cdot(.6)^3\cdot(.4)]=4[(.3)^3\cdot (.7)]$

I do understand where the $(.3)^3$ comes from, that is $.5\cdot.6 =.3$,

In simplifying the expression as follows, I arrive at $(2\cdot.3^3)+(2\cdot. 3^3\cdot .4)$

It is from here that I cannot figure out how this simplifies to $4[(.3)^3\cdot (.7)]$ Can anyone help with this?