Atriangle has one angel that measures 51 degrees and one angle that measures 39 degrees. what kind of triangle is it?

Those two angles are complementary - which means they both give us 90 degrees. We know that all three angles in any triangle must be exactly 180 degrees, so the third angle will be 180 - 90 = 90 degrees. It means that our triangle is a straight triangle. The figure will look more less like in the attachment.