You basically use the formula height*base/2 to find the area of the triangle. For instance, let's say a is your chosen base, which has a length of 7. You then use the pythagorean theorem of the right triangle (which is formed by splitting the triangle in half), which is a^2+b^2=c^2, and you substitute half your base for a and the other length (8) for c, which is the hypotenuse of the triangle. Note how this is all being done to find "b", which is the height of the triangle, which will then help you substitute all of your known values into the area formula of a triangle to answer your question. I'm not sure if b=141 degrees would have an impact on this question, but I hope this helped you in some way.
If you covert this into a mixed fraction it would be 75/4 (4*18 is 72 then add the 3 in the numerator) then divide, 75/4 = 18.75 (sorry if explanation is bad)
