Karen says every quadrilateral triangle is acute is this true explain

Karen is right; ever equilateral triangle is acute.
Equilateral triangles are also equiangular, because each side length corresponds with the angle length across from it. 

We also know that the angle measures of a triangle must add up to 180°.

Therefore, if there are 3 equal angles in a triangle of 180°, each angle measure is 60°. 

60°>90°, which means all equilateral triangles are acute.

Hope this helps!