Question

If LN=6x-5, LM=x+7, and MN=3x+20, find MN.

Answer 1

$LM+MN=LN$

$x+7+3x+20=6x-5$

$4x+27=6x-5$

$4x-6x=-27-5$

$-2x=-32$

$x=-32:(-2)$

$x=16$

Therefore

$MN=3x+20=3⋅16+20=48+20=68$

Answer: $MN=68$.