let
b------> the base of the triangle
h------> the height of the triangle
we know that
area of the triangle=b*h/2
h=b+8-----> equation 1
area=104.5 in²
104.5=b*h/2-----> 209=b*h-----> equation 2
substitute equation 1 in equation 2
209=b*[b+8]----> 209=b²+8b-----> b²+8b-209=0
using a graph tool---> to resolve the second order equation
see the attache figure
the solution is
b=11 in
h=b+8----> h=19 in
the answer is
the base is 11 in and the height is 19 in
