Question 890855
Imagine or draw this:
Triangle with base side 100, on the left a side making angle 60 degrees with the base, on the right
a side making angle 50 degrees with the base.


The vertex opposite of the base side is angle of measure {{{180-60-50=highlight_green(70)}}} degrees.


Law of Sines can give either or both of the non-given sides.  Picking the side on the left,
{{{sine(50)/L=sine(70)/100}}} where L is the length of the ungiven side at the left of the triangle.


{{{L/sin(50)=100/sine(70)}}}


{{{highlight_green(L=100(sin(50)/sin(70)))}}}


The question's meaning is to find the length from the 70 degree vertex to the base side,
which the altitude from that vertex.  This cuts the triangle into two right triangles.


Altitude is {{{L*sin(60)}}}, basic trigonometry.
Altitude is {{{highlight(100*sin(60)(sin(50)/sin(70)))}}}.