The 2 smallest lengths in a triangle have to add up to be greater that the longest side of the triangle. In this case, the longest side is 20. The 2 smallest sides are 5 and 10. 5+10=15, but 15<20. This is why these 3 lengths can’t create a triangle.
The denominator( s ) we are given are
, and . The first thing we want to do is factor the expressions, to make this easier -

This expression is a perfect square, as ( x )^2 = x^2, ( 2 )^2 = 4, 2 * ( x ) * ( 2 ) = 4x. Thus, the simplified expression should be the following -

The other expression is, on the other hand, not a perfect square so we must break this expression into groups and attempt factorization -

Combining ( x + 2 )^2 and ( x + 2 )( x + 3 ), the expression that contains factors of each is ( x + 2 )^2 * ( x + 3 ), or in other words the LCM.
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Answer: 16
Step-by-step explanation: 20/2 = 10
10x=160
10x/10=160/10
x=16