Question 366099
We can express the original area of a triangle as
{{{A = (1/2)bh}}}
If the new base is 10% greater, the new b is (1.1)b.
If the new height is 20% less, the new h is (0.8)h.
Now substituting, we get
{{{A = (1/2)(1.1*b)(0.8*h)}}} = 
{{{A = (1/2)(.88)bh}}}
Notice how the original area is only 88% of what it was...
So there was a 12% decrease in area.