Question 1057115
Volume of A:  {{{36cm^2 * 8cm = 288cm^3 }}}

Volume of B:  {{{ 5cm*3cm*12cm = 180cm^3 }}}

When A is poured into B, that "subtracts"  {{{180cm^3}}} from A.   So {{{288cm^3-180cm^3 = 108cm^3}}} are remaining in A.   If we divide that volume by the area of the base, we'll get the height:

 {{{108cm^3 / (36cm^2) = 3cm }}}

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Ans:  The juice will have a height of 3cm in box A after filling box B.
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NOTE: this problem can also be easily solved using a proportion.  The {{{108cm^3}}} volume remaining is {{{3/8}}} of the original {{{288cm^3}}} volume so the height would be {{{(3/8)* 8cm = 3cm }}}.