Question

Why can equilateral triangles always be acute angles?

Answer 1

Because equilateral triangles can only be equal with acute angles

Right angles can not work because your triangle will end up looking like a square because squares have all right sides 

It is also not possible to put 3 obtuse angles either other wise it might end up in some weird shape

But acute angles actually makes a triangle not a square or some weird shape

You can only fit one obtuse angle to a triangle but your triangle will end up being a scalene triangle because you have an obtuse angle and to actually make a triangle you need to use 2 acute angles so that couldn't be an equilateral triangle because none of he sides are equally the same

Now with the right triangle you can only have one side of the triangle a right angle which mean the other 2 angle and going to be acute, but if you made all 3 angles right it will come out as a weird looking square unless you add a 4th right angle to it, but you want a triangle not a square

Now acute angles fits better with a equilateral triangle then right and obtuse angles, because you can draw 3 equal sides and it will actually turn out to be a triangle and not a weird looking square or shape

So equilateral triangles will always have acute angles because its the only way for it to have equal sides like its supposed too.

Answer 2

An equilateral triangle has equal sides and angles.

Since the 3 angles of a triangle ad up to 180 degrees, we can see why they must all acute by doing the math:

x + x + x = 180
3x = 180
x=60

Which is acute.